To add force you would put the body parts you want to have force on
body r_pecs
force 0 20 1
This will add force on my r_pecs, with no force in the x axis, 20 in the y, and 1 in the z
All objects are solid, worldbuilder only shows holograms, to make objects not move, you have to make them static, flag 8
To make the floor instagib, you have to make a large world object that is on the floor, and make it flag 6