To help understand this in the simplest terms, think of it as 40 years ago, and you are putting up a TV antenna with a rotator motor on your roof to hook to your tv set to get channels.
The satellite dish and lnb, is the "antenna" in this case. The FTA receiver, is the "tv set/tuner". You install the dish and aim it at a particular satellite (like turning an old-school antenna to aim towards the tower of a tv station). You then set the tuning parameters for that setup on the receiver, and scan for open channels. Once the channels for that satellite are scanned in, you can move the satellite dish to another satellite, and do it again.
That's the very basics. Also, you MUST have a clear view towards the particular satellites you want to pick up. These signals can NOT go through physical things like regular tv signals can. So, if you have a TREE between your sat dish and satellite you are aiming at, you will get NOTHING. If you decide to do this,
first thing is to read all you can on the forum. Make notes if need be.
Second thing to do, is a "Site Survey" to try to figure out where in your yard you could best place a dish to receive the satellites you want to receive. This site can help you figure that out:
http://www.dishpointer.com/
If you can do all that, you are 75% there... Then it's time to decide if you want to really do it, and what equipment you want to buy.