Take your shirt and lay it on a flat surface. If there is a logo on the shirt, turn it inside out. (There was a logo on my shirt, but it was pretty thin, and it didn’t affect the comfort of the shorts.) Put the pattern on the shirt. Make sure that there is enough room on the shirt for two of your patterns, because you are going to need four panels in all. Also, if there is a pattern on your shirt (like for example, the tie-dye on mine,) try to put your pattern piece on a part of the design you like best. Pin on the pattern, and cut it out. Repeat once. Now, you should have four identical panels.
Next, pair the pieces together so that you have two doubled panels, right sides together, and pin along the straight side that is across from the curvy one (see picture.) Open. Now you have your two panels