There are a couple of ways to do this. The two that I know of are called parallel and series connections.
The easiest is the parallel where you simply attach both pairs to the main speaker posts, that is the main and the smaller ones to the same post on each side. Doing this cuts the output impedance by half and may not be the best choice if your amp is not rated to handle this. The only amps that I would exclude immediately are tube amps which need all the output impedance they can get, and certain SS amps that warn against this. I had a Marantz power amp that specifically warned against it. The other less "amp taxing" method is called a series connection, which has one speaker connected in a chain with the next speaker in series. I don't remember the exact connections so do a search using that term and I am sure you'll find it.
The easiest is the parallel where you simply attach both pairs to the main speaker posts, that is the main and the smaller ones to the same post on each side. Doing this cuts the output impedance by half and may not be the best choice if your amp is not rated to handle this. The only amps that I would exclude immediately are tube amps which need all the output impedance they can get, and certain SS amps that warn against this. I had a Marantz power amp that specifically warned against it. The other less "amp taxing" method is called a series connection, which has one speaker connected in a chain with the next speaker in series. I don't remember the exact connections so do a search using that term and I am sure you'll find it.