If you create an advertiser account but you want to work as a publisher, you do not need to create a new one. To open an account for publishers, please do the following:
Go to your HilltopAds account;
Navigate to the My Account section;
Click on the check-box Show publisher account;
Click on the Update Profile button.
After that, all tools for publishers will be available for you.
Please note, if you open a publisher account, you cannot close it by yourself. To do so, please contact your personal manager.