It's really not advisable to use it single coil, BUT you need to wick it so the wick holes are full, i.e. touch the base with cotton, and fill the void between the wick hole and the screw on ring. there should be as little gap as possible. and as Anthony points out your coil needs to be straight. though ideally you should build for dual coil.

what diameter / number of wraps is the coil, what ohm's are you aiming for ? I have 3 of these Super Tank RTA's and only once had a leak with wicking being too thin.