You can't really restore patina, which is the result of years of handling and use. What you can do, if you want, it to have the gun professionally reblued. That will not return it to its original appearance, but it will make it look better.
Trouble is that with all the environmental and employee protection laws, not many small gunsmiths still do bluing. You can use an internet search to find those who do, and send them the gun (you can mail a rifle to an FFL holder), or you can talk to a local gunsmith about who they use for doing that work.
One approach, but more expensive, would be to have a professional restorer, like Turnbull, really do a nice job on that gun, making it truly look like new.