Keeping the humidity up when maturing cheese can be difficult, especially if you are maturing cheeses in a large fridge which can dry the cheese out.
For the small scale cheesemaker, the best way to keep up the humidity is by using a Mad Millie Maturing Box. These airtight containers with a rack at the bottom ensure the humidity stays high while air can circulate around the cheese while it matures.
If you need to increase the humidity - you can add a wet paper towel (ensuring it hasn't touched anything else or introduces new bacteria). You can change this every so often as needed or remove once you have the level you need. You should not have condensation dripping down the sides - this is too humid.