You can only choose pictures that are max .05 mb so you kinda have to compromise with size and quality.
Anwyays this one should work:
https://i.imgur.com/8ii0pc7.gif
Top left, click on the arrow next to your name your name > Account Settings > Overview > scroll down and click on Configure next to "Steam Integration" > Sign Out
Try Shadow Play, that way you can avoid continuous recording and just hit a button whenever you need to save the past 10 minutes (could be any amount of time you specify in the settings)