chayan hrvoje_hr's method is not well supported, because it will be extremely difficult to utilize extensions in this manner (most users find the vanilla Flarum requires additional extensions to meet their needs). I recommend you try Pockethold as tankerkiller125 described, or contact your host to see if they can make accommodations for you.
There's also FreeFlarum.com if you are just interested in trying out Flarum for now.