After you've logged into the Mobile App, click on "Check Deposit" in the bottom menu.
Select the account you want to deposit the check to and enter the amount of the check.
Once you've entered the amount, an option will display to take a picture of the check.
First, take a picture of the front of the check. Next, the app will ask you to flip the check over to take a picture of the back. Make sure you have endorsed the check and written "For Mobile Deposit Only" under your signature before depositing.