Here is some info for beginners to vaping.
A lot of med marijuana can be given through a vape pen, which is a device that takes a small amount of liquid, turns it into a vapor, then allows you to inhale this vapor in order to get the medicine into your lungs and bloodstream.
Here are some videos culled from YouTube that may help.
Basics: what is a vape pen? How do they work?
How do I inhale without coughing?
TL;DR: keep inhaling air after your hit.