Ok, this answer may be quite long…
With a body weight of 140lbs, you’re looking at a base metabolic rate (BMR) of around 1960 calories per day. That’s calculated by multiplying your bodyweight in lbs by 14, which gives a pretty good estimate.
To gain or lose weight, you need to eat more, or less than this. It’s very difficult to gain lean mass, so if you want to bulk up it may be best to accept the fact that as you try to gain muscle, you’re probably also going to gain some fat, but you can lose that again later (and you may lose some muscle at the same time, but nowhere near as much as you would have gained previously).
Now to start with you don’t want to eat above or below your BMR by more than about 500 calories. This just allows your body to get used to the change. The best way to gain lean muscle is to control your diet and work out optimally. You should be looking for about a 40/40/20 split of calories from Protein, Carbs and Fat.
Carbs and protein each have about 4 calories per gram, whereas fat has 9, so you’re looking for more like a 45/45/10 split in terms of grams of each macronutrient consumed. If you’re bulking you obviously need to be eating more than your BMR, so let’s add 500 to that, to get 2460. Now you want to try and spread this out over 5–6 “Meals” each day. This means that you’re looking for 410 calories per meal, which will be 164 calories each from protein and carbs, and 82 calories from fat, which is 41g of protein, 41g of carbs, 9g of fat.
The reason you want to spread this throughout the day is that you’re then keeping your blood sugar stable, which is good for a whole bunch of reasons.
You should be trying to cut out simple carbohydrates and (white flour, white bread, white sugar, anything highly processed), saturated fats from your diet. At least 50% of your carbs should be coming from fruit and veg, but mostly veg. Good fats can be found in nuts and seeds especially. Peanut butter is an absolute godsend so far as healthy fats and protein, but make sure you get “natural” peanut butter, which should contain as an ingredients list only: Peanuts, Vegetable oil (3% or less), salt. Most brands of peanut butter also contain hydrogenated fats, or palm oil, or sugars, or other nasty stuff. Also eating eggs and drinking lots of milk will help with this. You say you’re already taking protein supplements which is a good start. All of this will help you gain weight as cleanly as possibly (ie. lean muscle).
A huge tip I can give is to track your food on the “Daily Plate” website. http://www.livestrong.com/thedailyplate/users/myplate/
This is a site where you can search for various foods, add them to your “plate”, and see how your overall calories and nutrient ratios are doing. It helps an awful lot to track your food for a few days and alter your diet accordingly.
Once you’ve got your diet sorted out, you need to get with the exercise.
You need to be lifting weights 3 times a week or more. There are a lot of different routines out there, but I’m currently following this one with decent results:
http://goonlifter.wikispaces.com/sean10mm's+Modified+Starting+Strength?f=print
There’s a good write-up there, complete with videos of various lifts. This is about the most basic routine you can follow while still getting good results. If you have any questions about proper form etc. then there are also lots of videos etc. out there, so for proper deadlift form I think if you just search for “deadlift form” on youtube you can get some pretty good instructions.