You can define your own master here by selecting respective masters. AcTouch had already defined Account Masters and will not suggest users to modify the defined settings.
The user can use the same screen to adding and editing/modifying a Customer.
All the fields details are self explanatory.
Edit/Modify the existing Customer
For editing/modifying select from the drop down or type the character it will show the list by filter the list. Change the field which you want.