What kind of accuracy are you expecting out of it? After all, it is some 50-odd years old! If it gains a only minute or two per week, I think you're expecting too much.
My own Waltham that used to belong to my dad gains 15 to 20 seconds per day - and I'm OK with that. After a couple days or so I just set the minute hand back a mark or two.
If it gains something on the order of a minute a day (or worse), well, that could stand correcting! Try the cheap and easy fix first. When you take your watch off at night, store it so it either rests on the crown or so that the crown points straight up at the ceiling. In this position, the watch may slow down enough to counter any gain accumulated during the day's wear. Try this for a wek or two to see if the accuracy improves. If not, take it to a local watch repair shop to have it tweaked.
Theoretically you could adjust the regulator yourself to slow down the balance wheel, but I recommend against it. Without knowing what you are doing and without the right equipment it would be a long, drawn out matter of trial and error. It is way too easy to move the regulator too much (yes, I'm speaking from personal experience!!!) and make the watch even more inaccurate than before. Plus, you could slip and bend the hairspring coil.
Better to leave regulation to a pro.