The primer that the atty comes with will leave a bad taste in your mouth until it all burns off. That is why you blow out the primer in a new atty and and then re primer it with the e-liquid that you will be filling your cart with.
All you need to do is get a napkin or paper towel and with the atty over it blow into the large open end of the atty where you cart goes. Blow until you are able to get a clear path of air going. Then wipe off the excess liquid on the bottom of the atty until it is dry.
Then re prime the atty with 1 or 2 drops of your e-liquid, do not add too much or you could flood it then fill your cart and you are ready to go. If you do flood your atty, just blow it out like you did the first time, if it still not performing well stand the atty up, connector on the bottom, and let it sit for a day so that the excess liquid can drain out of it. If available you can also blow out your atty with compressed air. Ideally, it is best to re prime your atty with liquid every time you vape a cart dry.
Hope this helps.