It is supposed to go into the woolly part, you just have to put enough that it looks glassy (but not a pool of juice on top). There are some tricks, called cart mods, like the blue foam mod that make it wick the juice down much better (without flooding).
Dripping is another way to do it, where you put 2-3 drops right on the atomizer every so often. Some say this method gives better flavor, though it is less convenient as you have to drip more in very often. Too much will flood the atomizer, causing it to not work (or work very poorly) until you blow out the extra juice (or vape through it, if it's not flooded too badly). If you want to drip I would suggest getting a drip tip, these replace the cart and just have a bit hole so you don't have to take the cart off repeatedly to drip (you can make a quick one by hollowing out a cart).