Your profile photo is automatically pulled from the social account (Facebook, Twitter, Google, Instagram) you've used to register on YouNow.
You can, however, change your profile or cover photo by following these steps.
If you are on a computer
Navigate to your profile page using the dropdown menu in the upper-right-hand corner.
Once there, click "Edit Profile" to upload a new cover or profile photo.
If you are on a mobile device:
Tap the avatar icon on the app's tool bar.
From here, tap the gear icon and then tap "Edit Profile."
Tap on either your profile or cover photo to take a photo or select and upload from your photo gallery.