After selecting Services, Adding a new service, selecting Frontend and the latest release, you should reach the Frontend configuration menu.
Select Custom Personal (Slave) and give your Frontend a recognizable name. Then add the Backend Url you want this Frontend to connect to. In the screenshot pictured, it is the url to a SlapOS Master Dashboard. The backend url
points to this Dashboard. Set Custom Domain and Server Alias to the domain you want to use
then scroll down to the bottom of the page and (don't forget) to select the computer to provide the Frontend slave.
Click Proceed to continue and request instantiation.