I'm not in a dev PC so I don't have any of my files or programs. But I'll try to write what i remember:
1. Yes, include the "using Farseer Psycis" and some more libraries into the classes of your game which will use physic objects. My game uses that ones:
2. In the constructor of your main or game class write
World.Gravity = new Vector2(0f, 10f); //Which will create a world object with gravity. This is needed for FPE to work. All objects must be in a world.
And the for the ground you may use a just a line. This is done by setting a list of vertices (2 for a line, various for a shaped ground), and make a body using this list of vertices.
Something like this:
Body ground = new Body(World);
Vertices terrain = new Vertices();
terrain.Add(new Vector2(-20f, -5f)); //Vertice 1
terrain.Add(new Vector2(-20f, 0f)); //Vertice 2
for (int i = 0; i < terrain.Count - 1; ++i)
FixtureFactory.AttachEdge(terrain[i], terrain[i + 1], ground);
ground.Friction = 0.6f;
If you want to draw the ground I think you'll need the ground to be a rectangle (not a line), and set a texture to it. I'm not sure of this. Or another option for the ground is to just draw the texture in the same coordinates where you set your ground.
The you should have a ground. Now you'll need object to collide with it xD.
Anyway, you should take a look at the FPE examples (Downloads section). You should learn a lot from them.
If you want to email me you project I could take a look at them and set up the basics for you to continue. My email is http://img694.imageshack.us/img694/7789/emailcf.jpg