[Roadster]

Question for Battery Tender Plus use???

Just want to make sure I hook this up correctly. Received mine the other day, and would like to know if the correct way is to hook up "P" clip to the positive terminal and the "N" clip to a metal ground instead of the negative terminal. Then, again if I disconnect both terminals and install my "dummy" attachments, I can then hook up to the battery directly???
Just don't want mess up the electrical system on our engine.....
Thanks.........