You can 'drip' by putting a few drops of liquid directly on the atomizer bridge and then putting on an empty cart
with no filler. Then you puff. This means there is no liquid stored in the cart material so you have to drip every time you start running out of vapor (anywhere from 3-10 puffs, depending on your PV and liquid). Some people report better flavor and throat hit and it's easier to switch flavors this way.
You can fill a 'blank' cart by taking a new cart with new filler (which you can buy in a 5 pack from vendors) and adding your own liquid. Annah was asking how many drops to add to blank cart to fill it. This is what I like to do because I don't like the prefilled flavors for the most part.
You can also 'top off' a cart by taking one that you've been using and adding new drops on the top. I usually add flavor on top of flavor and make my own mixes. For instance, I may be
vaping peanut butter and when I get tired of that I'll add a few drops of chocolate. When I get tired of that maybe I'll throw on some coffee or vanilla. Anytime your atty seems to be getting dry or you're not getting vapor or flavor you can add some drops and top off.
Hope that helps clarify a bit mishelle. And welcome!