Welcome to the Handi-House Slim.

I have a few rifles chambered for the 45-70 and it is one of the more popular rounds on this forum. You'll get some good information about mounting the scope but not from me. I don't have scopes on any of my 45-70s as they are primarily short range weapons when used for hunting, not everyone will agree on that, and most traditional long range shooting with these rifles is done with the old style open sights. Leastways that's my take on it.
I do know the scope you have and it's a good one. Leupold has been making quality optics for many years, they started in the survey transit and water meter business, and their home office and manufacturing facility is a great place to visit.
Enjoy yourself as you learn to hunt, there is probably a rifle range or two in your area and you can usually hook up with some local hunters that are looking for a "newby" to help pack meat out of the brush.
Mike