Two chainrings, two cogs. The gear change: First, you need the wrench for the hub nuts. (Get good track nuts if that isn't what's on there now. These

https://simplybearings.co.uk/shop/pr...gle%20Shopping

should work but this is a bicycle with the standards bikes are famous for Wrench should be 15mm but again... I love the Pedros Trixie fix gear tool.)

Back off each nut 1/2 turn. Slide the wheel forward. Pick up the chain with the spanner end of the Pedros (not necessary but dirty fingers gets old). Lift it onto the smaller cog or chainring. Then the other. Slide the wheel back. Tighten nuts as you adjust chain slack. The Pedros is perfect for running the chain around the chainring keeping fingers clean and un-pinched.

If you are running a double sided (flip-flop) hub, it is well worth it to have a chain peg to hang the chain on as you flip. Easy way to make that is get a 5M screw (most common threads in a bike and nearly all fender eyes), I like pan heads. Get a nut also. Start nut on the screw then insert into the fender eye from the inside (wheel side) so it sticks out toward the wheel about 1/2 a cm. Tighten the nut. Hang the chain on the pan head.

My advice - don't even consider a quick release hub. Chain slack is important. You never want the chain to go tight. That makes your hub and bottom bracket bearings old very fast. Too much slack and chains fall off on rough roads. With a quick release (QR) you have to try to get the chain slack right and center the tire between the chainstays simultaneously. A necessary total of brains, coordination and sometimes luck is required and may not be present after dark in the rain. With nuts, you can systematically work the wheel forward and back and get both the chain slack and tire placement right, no brains required.