You don't hit the add container button ever again. Go to the Apps tab instead and feel the love (there's also a full manual / help text available for CA if you hit "Help") (side note: Even when adding through CA, that select template drop down will still display, but you don't select anything for it)
As to what to fill out for the settings of the templates, any additional settings, etc will be detailed in the support thread for the particular app (A support link will be listed with every app), but generally, all you will have to do is fill out the host mapping for the /Config folder (ie: the appdata path)
Also wouldn't hurt to peruse the Docker FAQ sticky