CubeBrick I'm assuming this is a question about FreeFlarum. This is a community-run service and they have a dedicated discussion here https://discuss.flarum.org/d/7585-free-flarum-hosting-on-an-expert-platform-by-freeflarum-com
I also know there's a help article about that specific topic on their website https://www.freeflarum.com/docs/how-to/advanced-setup/custom-domain/
