Hey Doug,
welcome to the highroad! I too camre here as a new shooter and its been hands down the best resource on the internet.
Do you have any friends that are into shooting/guns? I would check there first and see if someone will go to the range with you and give you some pointers.
Keep in mind that sometimes the Nagants can be not all that accurate. If you are shooting rough with it, try shooting it with the bayonet on too and see if that helps.
My first gun was an sks and i practiced shooting it at 25 yards when i first started out and moved backwards from there once i got better.
Also investing in a cheap 22LR rifle might be a good, inexpensive way to practice shooting a rifle and it is great for learning the fundamentals.
A used Marlin model 60 or ruger 10/22 will usually be in the same price range as a mosin nagant. I paid anywhere from 80$ to 120$ for my basic, barebones 22LR rifles. You can even put a cheap scope on it like this which will improve your accuracy.
http://www.crosman.com/optics/scopes/0410
Ive used those on my 22s and while they are not the end all be all scope, ive never had a problem with them and the price is certainly right!
Hopefully this helps and feel free to message me on here with any questions you have.