You'll need to set-up permissions for your users to be able to use ABM. Here's how.
Click Users & Roles.
Click Roles, then New Role.
Enter a Role Name and click the + icon next to the Access Account Based Marketing checkbox.
To select all permissions, simply check the Access Account Based Marketing checkbox.
Click the + to open the Access Admin menu. Check the Access ABM Admin checkbox.
Your new ABM role is now ready to be assigned to a user!