This is a 2 step process. First to enable charging of credit card for booking, then, setting the service treatment for designating pricing.
Enable Charge Credit Card for Booking
Click Setup
Search for "Custom Settings" or go to Build->Develop->Custom Settings
Click "Manage" for Calendar Config
Click "Edit"
Check "Charge Credit Card For Booking" checkbox
Click "Save"
Setting Service Price
Go to a Service
Click New Service Treatment button
Click the Treatment Code lookup button
Select the Treatment Code
Click Save