First you need to run "cd C:\Users\jsphb\Desktop\". Then you can run "java -jar forge-1.16.5-36.2.20-installer.jar". Sorry for the bad explanation at this point, I just wanted to use another word for running because else the text sounds unnormal. I hope it works
Edit:
Oh, I saw that too late
But one thing:
If you want to program mods or anything other with java, you need to know these three commands. You don't need to learn them, there are quite easy, but don't forget them:
<drive>: <- Changing the Drive you're in
cd <path> <- Changing the Path
java -jar <file with .jar at the end>: <- Running a jar file manually that is in the selected path
Just don't forget them, these three are the most important commands (and I think the only ones) you need for programming java