Pick a category, read the rules for the category, record yourself playing with either a camera on the screen or a capture card, upload the video somewhere, then submit.
https://www.speedrun.com/mk8?h=32_Tracks-150cc&x=xd1m7rd8-ylpm6vlg.p12z6d1x
Pick a game, read the rules, record a speedrun, and submit it to the leaderboard. If you have any specific questions along the way then drop them here. Have fun!
@TheMahr So to directly answer your question "How do you set that up?"—the site doesn’t currently support exactly what you’re trying to do.
One workaround would be to have runners put their completion percentage in the hours slot. Using your examples, those would read 15:30:00 and 20:25:00, so the 15% run would appear as better on the leaderboard.
Another way is just to make a regular category with whatever the the theoretical and/or achieved minimum is. Something specific like "15% Completion."
Welcome to the site. What game are you looking to request? If it’s a Roblox game, submissions go here and not through the Support Hub: