Sorry what stitch setting for satin stitch on a Janome 6500?

Question edited for clarity.
Please don't type in all CAPS, it is considered SHOUTING and is harder to read.

Sewing machine tension is a delicate tug of war between the bottom Bobbin tension and the Upper tension to put the loop between the 2 layers of fabric. You set the Bobbin tension first and the the top tension depends on the fabric and the thread used.

Your Bobbin tension is very very loose to be not tensioning at all or the top tension is too loose.

Adjusting The Tension - Janome Memory Craft 6500 ...

ManualsLib https://www.manualslib.com > ... > Instruction book

Janome Memory Craft 6500 Professional Manual Online: balancing thread tension, Adjusting The Tension. Correct Tension: The Ideal Straight Stitch Has Threads ...

Best video on tension

Manual and a video

https://www.google.com/search?q=janome+my+style+16

..

Set a zig zag stitch and then make the length short.

here is a link for a manual, see if it's the right one
http://www.sewingpartsonline.com/instruction-manual-janome-and-newhome-mc6500p.aspx

if it's not the right one then contact janome about a manual

Before you go changing settings... make sure you are stabilizing the fabric correctly. Towels especially requires a stabilizer on top AND on bottom.

Mark your garment with chalk taking care to mark the start point and end points and a straight line to follow. Set your machine up for a fairly wide bar tack (zig zag in place) Then position the needle left and set it up for a satin stitch (fairly narrow) slowly stitch forward until you get to the end mark. Then do another bar tack. At this point you move your needle to the other side and satin stitch in reverse until you get to the first bar tack.

I would test this on a scrap piece first. Then proceed.

As a general rule of thumb, satin stitch is obtained by selecting zig-zag, turning stitch width up to 3 or 4 and stitch length to 0.5. If you have a clear plastic open toe sewing foot, put that on to help view the area.

If you are doing applique (attaching pieces of fabric to another surface) with a satin stitch, you may also need to use tear away stabiliser underneath or interface the fabric first, it depends on what/where you are doing the satin stitch onto.

And a nice machine embroidery thread will give you a much silkier appearance than plain thread.

It depends on a couple of things. Depending on the fabric you're using you might want to use a stabilizer like an iron on tear away. If the stitches are bunching the stitch length might be to tight. Try going to 0.3. if the stabilizer doesn't work. With the stabilizer on, it will keep the fabric firmer so it won't pucker. Make sure you have the decorative stitching foot on the machine with the little indentation for the satin stitch to ride in. If you have the wrong foot on, this will cause bunching too. Let me know if this helps.

the lock button is stuck on the front n of you mech.

Try using the zig-zag setting, but adjust the stitch length to .3 or .4 (very small).
good luck!