Try "googling" Instructions + t-shirt quilt.
Basically you cut apart the jerseys and iron on light non-woven interfacing to keep them from stretching for whatever logos, etc you need for the quilt. Be very careful as some of the lettering will melt, so remember to use a good press cloth to protect them (and when pressing blocks).
Otherwise they usually handle well and should make a nice soft quilt. You can use the plainer parts of the jerseys for borders or spacer blocks.
If you have a jersey that is a mesh you can try to match the colour in broadcloth or cotton and fuse that together.
These are lots of fun to make.