ok - so you've got a rifle for free. That might be the best kind.
Now you need an inexpesive scope. Based on this article:
Low Priced Long Range Scopes
I bought a Bushnell 3200 10x with mil-dot reticle. Mounted the scope on my 308
My 308 1k Rifle - The Evolution Continues!
Used it to kill a ground-hog at 810 yards. If you read through the description of my 308 you will learn some of the basic things you can do to help improve the accuracy potential of your rifle.
I don't think mil-dots are optimal, but you can learn to use them.
Once you've got a scope mounted, the next thing to do is to start shooting. Read all the "stickies" at the beginning of this forum:
The Basics, Starting Out - LongRangeHunting.com Online Magazine and Forums
From there you will learn all the basic....trigger control, breathing, prone etc.
Once you've done your reading...go shoot. Then come back here and post your questions.