Can somebody please teach me how to use this? Also how do you upload game recordings from your PC?

Hello there!

First off, if you need a place to upload your videos I guess Youtube would be as good a place to start as any.

Once you have your recorded runs uploaded to a site, you can submit them to their respective game's leaderboard. In general, when you submit a new run to a leaderboard, you'll be presented with a form of sorts with a number of fields such as Category, Final Time, Platform (Console/PC) and Video Link, amongst others. In this last field I mentioned, you can just put your video's link so that mods can personally verify your run.

And that's all there is to it really! You are welcome to join in on discussions on the forums too if you wish as well.

PS: Did you have any games in mind or are you still searching for a game to run?