As shown in the photo, cut a small block of plywood and fasten it to the center of the bucket lid. Using a hole saw or jigsaw, cut a hole through the plywood and lid that another piece of PVC pipe will tightly fit. Again, caulk with silicone. Use plenty - It is what holds the pipe in place.
The hose from the vacuum goes here. The pick up hose goes to the side connection. You have to come up with a second hose for this; I used a pool skimmer hose that I had. Then again, I keep all kinds of junk - you may not. In that case, you will have to buy something that fits.