Register new account on our support forum: https://support.cththemes.com/wp-login.php?action=register
You need to use Envato’s purchase code to verify purchase then complete the registration process.
Login with your account then select purchased theme’s forum on the right sidebar to enter that item page.
For example: if you purchased CityBook – Directory & Listing WordPress Theme , find and select CityBook – Directory & Listing WordPress Theme forum as shown in the image below.
Then use editor at the end of the forum page to create new topic:
Notice: It’s theme-based support forum. You cannot purchase another item to claim support for the other item. So please make sure that you are posting topic on right theme forum.