Now it depends if you want to use mods or not. If you want to use mods, you would use forge (or smth similar, just adjust the following steps) Thats it, make sure to have the path to your servers ...
OptiFine 1.15.2 HD U G1 pre16 OptiFine 1.15.2 HD U G1 pre17 I did the exact same setup on my laptop and that worked flawlessly. I'm unsure why it's not loading via my desktop.