You can find a video guide for creating and assigning rate cards in the second half of our "Creating your first customer and rate card" video guide. Relevant information starts from approximately 5 minutes in.
Watch on Youtube: https://youtu.be/Y316ZC5qjCE?t=299
The Xero related components of this video only apply to partners using Xero for their billing platform. Partners using Octane or Nice should disregard the Xero-related steps at the end of this tutorial.