If you have never used FaceBook ads then you will need to setup your Business Manager Account within FaceBook first. The below link will provide you with the steps on how to get this set up.
Once you have created your account to use with your business, you will need to complete the instructions here:
This second link will guide you through the entire setup process necessary prior to integrating with our platform. Once this process is complete you will be subject to a grace period while Facebook audits your account to be sure you will adhere to the policies you agreed to in the TOS.
You will not be able to create a custom audience until after this grace period has passed. More information on this can be found in this article: