By default your avatar is a blue icon with your username's initials. To customize your avatar:

In the app

  1. Go to the main menu and select your profile.
  2. Select the Edit button (or pencil icon).
  3. Select your current avatar again, or select Edit avatar. From here you can take a new photo or choose a previously saved photo.

In the web version 

  1. Select your current avatar to display your profile settings.
  2. Hover over your avatar and click Change avatar.
  3. Browse for a new photo and click Open.
  4. Click OK in the confirmation box.

Update your Group's Avatar

To update a group's avatar, go to the group's chat settings (rather than your profile settings) and then follow the rest of the steps above.