You mean the "rack" like thingy? You need to put a kobold in there and then physicaly push (yourself or with item) the drum looking part. It will then push out the "male kobold product" from the dildo into the chained kobold.
Its Main purpose is to increase the Stomach size both with the bar and the Kobold itself. Once you set a kobold on there you can pump various liquids into it by running into the middle part. id recommend filling with water first in order to test this out.
