When we look through the eyepiece all we see is black like if something is blocking the mirror but there is nothing there. And our sky tour doesn't even turn on with new batteries or anything.

Did you set it up according to the provided instructions?
Do you have a low power eyepiece inserted at the viewing end?
Have you aimed the telescope at the moon as a basic test of
visibility?
If your telescope is not properly aimed at the target (a star or a planet, or other object in the night sky) then you will see nothing.
If the power of your eyepiece is too large and your telescope aim is
not "dead on", then you will see nothing.
Have you tried using the scope in the daytime? Do you see anything?
Aim at a specific object, or section of an object, like the top of a lamp-post about a block or two away, and see if you can focus on
it the eyepiece.
You really need someone at your side who has experience in using
astronomical telescopes. That would be the quickest way to solve
any problems you have.
Unless your question is very specific, and unless you provide as
much detail as possible about your problem, it will be difficult for
anyone to provide you with speecific answers that will help you
solve your problem.
joy,
walt

You can buy Eyepieces and Barlow Lenses

I recommend buy on
http://www.bhphotovideo.com/c/product/765322-REG/Bushnell_789931_Voyager_Sky_Tour_700mm.html


Is important for people who share their knowledge, know your comments.
If the answer is helpful, rate my answers

This is a great scope. I have a much smaller version :)
1. Take it out on some dark night. 2. Let it auto-align 3. Select something to look at using the AutoStar II 4. Press Go.
Gander at the wonders of the universe.
In the AutoStar, there is a program called Sky Tour. This will pick some things out for you.
Start with a "wide" eyepiece - to see more of the sky. Work your way to high powers as you need or as sky conditions permit.
Goto a few local "star parties".

This is a REFLECTOR style telescope. The end with the focuser and the eyepiece is pointed UP. the mirror is on the bottom of the scope.

Take the scope outside during the daytime and practice focusing on a distant object using the eyepiece with the LARGEST number written on it.

The PICTURE shown above really makes me laugh. The scope is mounted BACKWARDS in the picture above, and is pointed toward the GROUND not the sky. Even FIXYA puts them on the mount backwards!

Look at this picture. See how the eyepiece and focuser are on the end pointed toward the sky. The MIRROR is the BOTTOM of the telescope:

https://www.highpointscientific.com/store/viewItem.asp?idProduct=385

I believe your scope is mounted backwards just like the picture FIXYA applied to your question!

What I believe you did was mount the scope UPSIDE DOWN. If it looks like the picture in your question the eyepiece and focuser end is pointed UP the mirror is on the bottom.

Turn it around and take the lens cap off.... this end is pointed toward the sky.

The front is the part where the eyepiece and the focuser happens to be. That is called a REFLECTOR style telescope. Light enters the front of the tube and bounces off the mirror in the bottom of the tube. There returns and bounces off the small secondary tilted mirror out into the focuser and eyepiece. There should be an easy to remove dust cap on the front end near the focuser. That end is pointed toward the sky.

These types of scopes should be checked for collimation to determine if the optics are all lined up.

Watch this video:

http://www.andysshotglass.com/Collimating.html

Try to find a local Astronomy club and get them to help you with the telescope.

Verify that the mirrors are aligned; look through the eyepiece holder (without an eyepiece) and you should see the main mirror with your eye looking back from the center. Ensure that there are no filters on the eyepiece, and use the lowest power one to begin (longest focal length).

Put the eyepiece with the largest number written on it into the focuser. During the daytime practice focusing on a distant object. The moon should be your first target at night.

If this is a reflector telescope, the FOCUSER end is pointed toward the sky. The mirror is on the bottom of the tube.

The focuser and eyepiece are POINTED UP toward the sky -- the mirror is at the bottom of the tube.

Put the eyepiece with the largest number written on it into the focuser, and during the day time, practice focusing on a distant object.

Did you start by using your lowest magnification eyepiece? Until you get used to that one it's almost impossible to use the higher powered eyepieces. I was looking too high in the sky and with too much magnification and was having the same problem. Find something like the roof of the garage and then gradually sweep the sky just above it slowly. --- If you can see only black during the day too - there is possibly a misalighnement of mirrors - you can buy a collumating kit from celestron.com - hope this helps.