This is a 2 step process. First to enable charging of credit card for booking, then, setting the service treatment for designating pricing.
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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"
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Setting Service Price
Go to a Service
Click New Service Treatment button

Click the Treatment Code lookup button

Select the Treatment Code

Click Save
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