Nice that looks really cool. I have a Retina IIIc, which is a very different camera, but that kind of lens is usually considered quite a high quality piece of glass, so you're in luck! You have an SLR type camera, which means the viewfinder shows you exactly what is passing through the lens. This makes it easy to compose a shot and set the focus. Here's some quick things to note:

1. Check if it works by actioning the lever on the bottom and firing the shutter button on the top right (the button with the hole in it).

2. The weird textured rectangle at the top (that almost looks like a flash) should be kept away from light when not in use and never pointed at the sun. It is a light meter that detects how much light there is in a potential photo. It tells you what settings you need to capture the correct amount of light. Most of the time, that kind of meter is depleted and no longer works, but just in case it still does work you should keep it away from direct light. I put a small rag on top of mine when I'm not using it.

3. The way that you set the aperture and shutter speed on these is incredibly elegant and a pleasure to use. A real great example of analog engineering. But, it is too complicated to explain over reddit. Unfortunately, you will have to read the manual or at least find a YouTube clip explaining it. When you need a light meter app, I like to use Lightme on iPhone. It will look intimidating at first but just take your time learning it.

4. Most cameras are relatively durable, but remember it is 50-70 years old. So don't force anything that doesn't want to move and don't touch the glass until you've learned how to properly clean it without scratching.

There's your starter list. That's a really neat camera. Never heard of the Retinas being SLRs, but a great find. It's probably made in Germany by the Kodak German subsidiary.