The metal drain pipe is pretty stationary. The plastic or pvc pipe that slipped off the metal drain pipe should have a plastic Locking colar on it. This locking nut or colar should be loosened a bit. Then push the entire locking colar with the rest of the pvc pipe connections up on the metal pipe and then tighten the colar with channel locks or vice grips or something that you have around there wide enough to span the locking nut.
Gently turn it clockwise until snug.
Now, if the locking colar or nut came off, then we have another scenerio. You will have the actual threaded nut or locking colar and you will have a nylon washer the diameter of the metal pipe from the bottom of the sink.
If this happened, do this, Place the locking nut or colar up on the metal pipe and hold it there. Then insert the washer also over the metal pipe and push it up to the locking colar or nut on the metal pipe. There are two ways to push this nylon washer up on the pipe, one is right and the other will not work. The washer is the shape of a triangle if you will. Insert the washer on the pipe with the broad or flat side of the washer up on top. this would allow the tapered edge to be pointed down to the floor. Now, run up the rest of the pvc pipe that contains the trap up on the metal pipe.
Now you should have the following run up on the metal pipe. First, the locking colar, then the nylon washer, now the bottom pipe.
Now, mate up the locking colar and the washer with the bottom threaded pipe and tighten up. Make sure not to cross thread.
Snug it up tight with whatever tool you have that will open its jaws enough to tighten the locking nut or colar.
Now, turn on the water and you should be set.
If you have a drip, then tighten the locking colar some more, do not crank down on this or it will break.
Hopet this helps. Your husband should be more understanding and helpful.