You can edit your profile picture in your account settings.

Once you're in settings, click the Profile tab. In this section you'll see a green button with the text Change Avatar. Click this button to upload a new profile picture. All uploads have a max size of 1MB. If you're file is too large, we suggest using a tool like https://tinypng.com/ to reduce the size.

Once you're happy with your new pic, make sure to save your changes!