Before you log in to UltraAV on Android, you will need to activate your account and set a password. Please follow the instructions in the article How do I set a password for Ultra Antivirus' products? if you have not done that yet.
To log in to Ultra AV, first open the Ultra AV app.
When you open the app, you'll be presented with the Scan screen. On this screen, click the Profile button in the upper-left corner.
This will take you to the log in screen. Enter your Ultra Antivirus login credentials to log in.
You will now be logged in to UltraAV on Android.