Filling Bottom Coil Clearomizers is relatively easy you just need to be a bit careful
Remove the base and put it aside, tip the clearomizer upside down and fill into the side of the clearomizer. Do not get any liquid into the center hole. Then make sure you put the base back on finger tight and you are done.
The difference bewteen a top coil and bottom coil is show in the image below, if your drip tip comes off it is generally (but not always) a top fill clearomizer, if it does not a then it is always a bottom coil clearomizer.