I'm a little confused about the circumstances of this lease... You have been lessoning , but do not know how to tack/lead? (That wasn't meant to sound rude, I'm just trying to understand).
If that's the case (it may not be, I could be reading wrong!) then I'm guessing that you arrive to an already tacked horse. I would say learning these basics, from your trainer, is absolutely step one. They will be able to show you everything you need to know, plus make you aware of any quirks your lesson horse may have.
Since it is, indeed, a lesson horse... You really shouldn't be worried about anything /too/ crazy.
Enjoy your new lease! We'd love pics! <3