It doesn't matter if you squat less than you bench - you can work on that, and everyone starts from somewhere.
If you have issues with your knees, then you probably need to address those first.
If you favour your right leg, you might need to look at your posture and your hips - you may have an anatomical or functional leg length discrepancy causing this. If you favour your right leg re strength, then do some single-leg exercises such as leg press, etc. to start building your left leg strength up.
If you want to bring your legs up re mass and strength, then you first of all need to be EATING for it. As far as exercises, stick to doing variations of squats - front squat, back squat, sumo squat, etc. I would suggest starting out at 3-4 x 10-12 reps for a few weeks, just to get used to doing the exercise and do 6-8 sets in total of 1-2 exercises a session (i.e. front squats 3 x 10 and then back squats 3 x 10), focusing solely on your legs and nothing else in that session (or you can add in a few abs/core exercises at the end of the session). You may also want to add in a couple of sets of something like lunges or leg press after doing your squat sets - but not a necessity, and this is probably best after a few weeks. Make sure you have ~2 days between Legs' sessions for optimal recovery.
Also make sure you're doing deadlifts on back day.