You can go on line and there are many sites to tell you how to make a tee shirt quilt. I just made my first one and my advice to you is to fuse each sq. on a piece of muslin for the backing, after I made mine I learned of this and think it is a good idea
and also if you are going to quilt it don't quilt in the fusible squares. your thread will break all the time. I just did quilting on the sashings.
This of course was just how I did it there will be many answers to this question I believe.