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 large plastic container with loose lids and a plastic drying rack in the bottom.
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.