Go to Coin Stats app Altfolio tab, scroll far to the right and click Add new portfolio by Selecting Exchange (API KEYS).
Tap to choose Coinbase Exchange and try to Authenticate.
Then Login to your Coinbase account
Verify your account with a code generated by your phone.
After clicking Add your Coinbase portfolio will appear in your Coin Stats app.
Refer to support in case of further questions. Hope you'll enjoy.