You can update or remove your profile picture in the 'My profile' section of the app.
Tap on your username or photo in the top left of your Home Screen to open the 'My profile' page.
Under the heading ‘My Accounts’ you will see a list of each currency for which you currently hold funds:
Alongside each currency will be the total amount of funds which you hold for that specific currency. If you tap on the currency you will be taken to the ‘Add Funds’ screen for that currency.