Well I'm 5ft 6inches tall I weigh 146 pounds and I'm skinny but I have a big butt, and I have really skinny legs, I would like to make them thicker and bigger. I eat a lot and lay down, I eat junk food and fatty foods such as fried and I eat a lot of fast foods but I still won't gain any weight what should I do?

1st, STOP what you are doing, everything you just wrote is very unhealthy.
--It sounds like you have a high metabolism . Which is what most people wish they had.

I suggest speaking to a trained Professional (gym trainer perhaps.. or nutritionist).

There are exercises along with supplements to help build muscle to "thicken" you up, loading up on junk and not exercising will eventually lead to UNWANTED effects. . Like your Stomach, Arms, Face, Legs, Feet etc.. Getting fat a flabby.

You sound like you have the perfect set-up for being fit and active but are failing to get healthy.

---- Your issue isn't your legs, Learn to Love your Butt! Tone that sucker!

I am 4.9 and weigh 108 pounds. I am very skinny from my legs. I eat healthy and I exercise by doing a 3-mile run, 3 to 4 times a week. I still see no difference in my legs. What else can I do?