when I place some models in radiant such as weapons and other various models its just showing up as red squares. Can someone tell me what im doing wrong?

Check the error console attached to the bottom of the window - it will tell you if something is missing/broken.

the KVPs are

model
xmodel/(name of xmodel here)

If it doesnt show up your not referencing it from the correct folder or it doesn't exsist as an xmodel.

Same thing will happen if u reference a prefab that isnt where ur telling radiant it is...

thanks guys now i understand from generals reply, all it was telling me in console was load "model name" failed. I got it now thanks