When you first bring up the mobile app touch the 3 bars on the left side of the top banner. The banner should change to have a gear symbol on the right side. That is the settings. I have my signature set to custom but it still won't show up on the mobile app like it does on the website.
Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD 4dr short bed Duramax w/allison
Reese Fifth Airborne air ride king pin coupler with Sidewinder