This is your only post, so not much to go on as to your experience and knowledge. Hopefully this doesn't sound patronising and assuming you are totally new to vaping. The iStick is your battery, could you tell us what tank you are using on it, or as Whiskey suggested, a picture?
With most tanks you have to make sure the liquid goes down the sides and not in the centre chimney. It's always good to make sure the coil is firmly screwed in before re-attaching the base. Most coils have a rubber seal that goes between it and the central chimney to stop your liquid getting through, occasionally this seal can come off. You also need to check to see if the wicking material in the coil is still in place (again a picture of the coil would help).