How to setup a CallRail integration
First, navigate to the home dashboard for the campaign where you'd like to connect this CallRail integration. Then, choose "Call Tracking --> CallRail" from the dark navigation bar on the left-hand side of your screen.
Next, click the link in the middle of the screen that says "Setup CallRail".
In the next window that appears, enter the CallRail API key for the customer account that you would like to connect, then click "Save". This article from the CallRail Knowledgebase provides details on where to find your API key within their interface.
The integration will then be complete, and your client's CallRail metrics will then be imported and displayed within their campaign.