I think it’s pretty obvious that the OP is saying he want’s to gain 12 pounds in 12 months but at that time have the same body fat % which he has now. IMO it’s a very good goal and at his age and weight is a realistic goal.
I wouldn’t focus on trying to get a pound each month though as the body doesn’t always work in such time frames. Sometimes you may stall whilst at others you will grow. It may come in spurts and 12 pounds is a hell of a lot of muscle to gain but it is a very worthwhile goal and something to aim for.
The main area to focus on is nutrition. If you aren’t using a food tracker then start right now. myfitnesspal is a very good one and it counts your calories and breaks it down into macros. Plenty of great information on this website to give you an idea on how to set up your macro ratios.
The main thing though is to find what your current base is then you must add to it. How much you add again is something you need to do some research on and this site has plenty of information on that very subject.
Don’t try and maintain a 6 pack or do anything silly like that. You will gain some fat in the process but that’s fine as you will also be gaining some muscle.
The next question is what program to do but if you have been training for 7 years then you should have a pretty good understanding of what exercises work best for you. The key thing here is to pick a body building program and not a program that is strength based or power based or performance based etc… Plenty of good programs on this website and there are E books around with hundreds more. Clay Hyght has an excellent book with at least 30 programs in it. John Meadows has programs on this site that are size based and so on. Eat for size and train for size and at your age your body will do the rest and grow.
Good luck in your quest for muscle.