From the left-hand navigation menu select the Customer menu item:
This will bring a list of the customers for the business. Click on the pencil icon 
You will go to the Customer details page with the following tabs:
Profile: Name and contact information (email, phone, address)
Pet: Manage the customers pet information
Additional: Tax, Internal notes and access instructions
Custom Form: Any custom fields that have been created for the customer profile
Billing: Customers can save upto two credit cards here.
Go to the individual tabs to edit the information and than click the save button to save the changes made.