If you plan on animating the character, make sure all the mesh parts are welded correctly with all the joints and stuff. If you are not planning on animating the character or making it move, then simply anchor all the mesh parts in the model.
If you made this in a 3D Modeling software like Blender, then make sure all your welds, bones, etc. are all there. If you got the model from somewhere online, then you might have to rig the character yourself.