Once you have been approved for a Zip account, to sign into it simply open the Zip app and enter your phone number to receive your verification code. Then, enter the code in the text you receive in your Zip app.
Once logged in, select the Account tab. Here, you'll be able to set PIN and Facial ID as quicker, more secure login methods.
To set your login PIN, select Change PIN and enter your desired 4-digit PIN number. To enable Facial ID, simply toggle the Enable FaceID option.