I highly doubt you have 77 GB of free RAM. This value is how much RAM Minecraft (or rather Java) can use, not disk space.
You were right here, I was looking in the wrong place.
You can test if you did it correctly, by running the server and then using a port-forward tester like http://www.canyouseeme.org/ to see if the port is open.
The tester says it timed out. I'm using my IP address and the 25565 port.
You can set the port that the server listens on in the server.properties file. The default is 25565.
It says it's a .PROPERTIES file, and my computer can't open/edit that file type, to my knowledge.
Run a game on the same computer and connect to localhost. If you can connect, the server is running.
How exactly do you do that?
The IP of the server running the game. If you are on the same Network (then you don't need to open ports in your router, either), use the local IP of the computer. On Windows you can use the ipconfig command to find it. If you want to connect to it over the internet (this is where you need the port-forwarding), you need the public IP of your router. There are many websites that tell you your public IP, one of them is https://www.whatismyip.com.
The computers I am trying to connect to are not on the same network, and, like I stated above, my IP address is not working.