Hi, welcome to the forum! Glad you joined!
Why? If you don't know, ask. it's what the forum is about.
I'm not familiar with the Mini but I have an older model of the 1588. With the 1588 you put water in one or more of the reservoirs in the bottom, close the lid, and wait. If you spill water and get areas wet that you don't want the humidity can spike up until that excess water evaporates. What controls humidity in that type of incubator is the wet surface area. To stabilize the humidity you have to wait until the only surface area wet are the reservoirs you filled.
I don't see a turner in that 1588. One time the humidity in mine dropped lower than it should have been. The cord that goes to my turner was not in the slot properly so it had the lid cracked, which allowed moist air to escape. So make sure the lid is on correctly. If you are using it as a hatcher you do not need a turner.
I don't know enough about the Mini to speak to how to stabilize the humidity other than to crank it up and follow instructions, then see what happens.
You did not ask about adjusting humidity. The way I do that with my 1588 is to fill different reservoirs. When I first got it and before I used it I ran it with different reservoirs and different combinations of reservoirs filled and kept notes to see what the differences were.
Different air temperatures and different moisture levels in the room the incubator is in can give different results inside the incubator. Sometimes I make adjustments on which reservoirs have water in them based on what I see. But I try to keep the incubator in a stabile location to minimize that.
Good luck!