Stair machine is a monster!

You guys doing that 1 hr stair challenge are absolutely incredible! I'm 300 lb and finally got the courage to try the stair machine tonight and omg that thing is a monster. 7 minutes is all I could take after a few clicks up in speed. I'll keep trying! Any tips for working my way into being more successful on that beast? Thanks for the inspiration. This is a lovely group of people in this sub.