I want to assign my purchased domain but when I select the "Used Purchased Domain", it doesn't anything in the drop down menu.
Did you just purchase the domain? If that's the case, you might need to refresh your account and then try to add the domain. If that does not work, what's the domain name?
How to refresh my godaddy account? @charminglygeeky
Sorry, I did not mention in my previous response, you will need to reach out to our support team to do so.