In order to register an email address, please follow the steps given below on InTouchApp installed on phone.
Step 1 - On the Calls/Feed Tab, click on your profile picture at the top centre of the screen.
Step 2 - On Account screen, click on See details.
Step 3 - Click on the right overflow icon.
Step 4 - Select Edit.
Step 5 - You will be re-directed on the Edit screen, update your email address on the screen.
Step 6 - Once done, click on the Right tick at the top right corner of the screen.
Step 7 - You will get Email Verification link "Please verify your email for InTouchApp account" via email.
Step 8 - Click on the link to verify and your email address is registered in your account.