The bottom has a press fit into the sides. Get a good light & if your eyes are like mine, your reading glasses. You will find where the tabs are to pry it open. Once you get it apart, plan on a good soak in your favorite degreaser for a few days. It will clean up .
If you can salvage the old mesh, soak that along w/ the canister. If you need new mesh, plenty of places have it. It comes in a roll. The filter takes 2 rolls. Steel wool won't work.
Hint: Wrap the mesh around the breather tube (it is the same diameter as the tube inside of the air cleaner) Or, use a tube of caulk. Place the breather tube (or caulk tube) against the tube in the air cleaner & slide the mesh off, into the air cleaner. Otherwise, getting that mesh rolled tight & back into the air filter is like getting used toothpaste back in the tube.
Don't forget to replace the cork gasket in the bottom of the canister. If you don't, it will suck air & leak oil between the cup & canister.