(1) bobbin does not supply thread (2) cant switch to stitching mode

If the machine has been used, it may be worthwhile to take it for service and make sure the machine is operating properly. Nothing is more frustrating to a new user than trying to make a faulty machine perform. (One assumes a new machine should be ready out of the box, but frequently there are defects or mal-adjustments.

A couple of simple hints:
Install a brand new needle every 8 hours of sewing use. A needle is a very inexpensive fix for a lot of sewing problems.

Verify that the needle is installed facing the correct direction. Needles have a flat side that needs to be installed in a certain direction or the needle will strike other parts of the machine.

When threading the top thread, ALWAYS RAISE the presser foot so the thread will seat properly in the tension disk. Start out with the top tension set at the midway point and then tweak it for your machine.

VERIFY the thread path is correct! A mis-threaded machine will cause a load of frustration!

Tension is accurate when the top and bobbin threads meet in the middle of the fabric.

Be sure to clean and oil your machine regularly. Use only fresh, good quality sewing machine oil and apply 1-2 drops each place specified (pg 76). The troubleshooting section is on pg 78 as a quick reference to any issues with the machine.

Here's a manual:
http://homeappliance.manualsonline.com/manuals/mfg/kenmore/15218_1.html

You may check with stores like JoAnn's if they offer beginning sewing classes. Stores will frequently offer classes, especially for children to learn how to sew. Adult education classes used to offer sewing courses. Even some craft stores offer classes.

Check out if the needle is faceing the right way, otherwise when the needle goes down it will be hit by the rotary hook when it starts comeing up .

If the needle keeps hitting at one place only, make sure the feed dogs are UP, these are the little teeth you see just level with the metal plate under the needle. If they are below the plate, you need to press a button or lever to bring them up level. Make sure your bobbin is wound evenly and not too tight, or loose, make sure you have inserted it into the bobbin case the right way round, with enough spare thread at the end, about four inches. Hold the thread coming from the NEEDLE in your left hand, do not pull too tight, just a little slack. It has to go down into the bobbin area and pick up the bobbin thread. Now turn the hand wheel at the right end of the machine slowly, until you see the bobbin thread come up through the plate. Pull both threads towards the back of the machine, and you are ready to sew. I do not know the Kenmore, but this is basic advice for most machines. Good Luck.