There is one block on audience tab called "Where to target". Under this we have an option of specifying details of URL where we want the pop up to be shown.

The website selected on setup page should mandatorily be a part of the one entered in the condition of URL with operators like equal to, contains, starts with, etc on audience page under "Where to target" block.

For ex. if on the setup page website selected is and on audience page if we try to use condition as URL equal to or  then it wont allow you to move to the next page by disabling the "save and next" button.