How can I bring down the humidity in my tent?

Get a small fan and leave it on in your grow room.

Buy dehumidifier, basic one (cheapest) for start or you could buy the one that can regulate automatically (let's say you want 50% when this is reached it will auto stop extracting moisture from air) note that you will have to empty a tank at least once per day. For more specific answer you really should tell us more about your setup like tent size, extractor fan, average humidity, in which stage you are in, etc... Relative humidity will be higher when you water the plants.

What type of setup do you have,a good extract and supply is a good start