If it's a 3-piece battery + atomizer (which they may call vaporizer) + cart...
And the cart pushes on OVER the atomizer... (how most super-mini ecigs are)
Take the cart off, stick a small unbent paperclip leg into the mouth hole and push up the
juice cup to when you can see it
You can add
juice to the stuffing in the juice cup, if needed reposition the stuffing near the top edge of the juice cup
If there is shredded foil around the juice cup I think you can remove that
Then you need to get the juice cup back down into the mouthpiece WITHOUT pressing on the stuffing. It may just drop back down nicely on its own. Else...
Some super-mini model carts come with a silicone plug - if you have on you can use that to push the juice cup back in since it should only press on the edges of the juice cup. If not, then you need to use the paperclip or a bit of dowel or something to get the juice cup back all the way down in there without pressing on the stuffing. I do not recommend using the atomizer to do it because it would probably push the stuffing in too far.
here is a video with a model where the juice cup drops easily back into the mouthpiece so you don't need a way to push it back in
http://www.youtube.com/watch?v=h0NpH2np89k