You'll need to set users up with a license to use ABM. Here's how to do that.
The number of available licenses will vary based on your subscription. If you need more, please contact your sales rep.
Click Users & Roles. Select the user to issue the license to, click the Issue License drop-down, and select Account Based Marketing.
Check the Enable License checkbox and click Save.
To remove a user's license, follow step 1, then uncheck the checkbox and click Save.