it's really simple, just easy to have this.
Step 1: What You Need
duct tape (optional)
Step 2: Fit the Sponge in the Tin
if you have the right sized sponge you don't really need to do anything.
Step 3: Mark the Back Where You Need to Cut.
Mark The Back then cut the sponge with scissors.
Step 4: That's It
its just a some sponge for cleaning your soldering tip. I had to use duct tape to help keep the tin closed, but if the sponge you use is smaller you may not need it.