Building up muscle is a slow process and typically slower for women than men. Generally speaking, you gotta lift heavy, & eat protein & calories above maintenance. (gaining weight)
You can build mass with bodyweight exercises but using weights will probably get more results...
Either way is gonna take months before you start to notice any difference.
Skateboard I got legs like a monster from skateboarding
There is a ton of programs you can find for female training. Both bulking and shredding plans for free can be found on bodybuilding.com. If you are fairly new, like 1 year or less to working out I recomend jamie eason live fit trainer. Check it out. You will learn a lot.
From my personal experience I highly suggest walking by that I don't mean using the treadmill not that it's not effective but I'm speaking about actual walking .See one of the most used and strongest muscles we have are the ones in our legs, and because of our natural tendency to be lazy we take every opportunity we can to skimp on using those we muscles e.g using elevators instead of stairs, driving a vehicle instead of walking... etc. So I'm not saying throw away your car and skip the elevator ride what I'm saying is to just keep those muscles active regularly and daily by taking daily walks now here comes the tricky part that many people fail to handle and that is not everybody has the ability whether physically or mentally to reserve some time each day just for walking. And the answer for this is that walking doesn't have to be a chore or a workout or anything that you feel you have got to do, rather it should be something where you wouldn't think twice about doing, and would probably do whenever the opportunity arrives. For me I do that by going each day from my uni to my gym on foot it's not a super long walk and not a short one but over time I have become used to it, at first I used to litrally suffer but now I don't really feel anything it's become second nature for me. Shit I've written an essay...
I bulked up my legs in about a month. I walked everyday, did different types of squats and lunges every other day, and proteins and fruit.
Our legs carry most of our body weight daily so they are fairly strong already. So in essence, bodyweight exercises would only help to tone up the already-strong muscles? Therefore, weights would be the best option as Patrick has mentioned. So if you got dumbbells, use them :)
So I've read the previous posts and some were okay, some were not. The best way to build up leg size is weighted squats and deadlifts. I come from a family of chicken legs, but my legs are like tree trunks oh and calf raises. Squats will do mostly upper leg and calf raises will finish off the legs. Plus squats give you a nice butt good luck