I am using a site called Flat. Can I use it for an arrangement?
My arrangement is for vibes, not piano. It won't show on the main site, correct?
Could I have a more experienced member of Ninsheetmusic look over it before I submit it?
Yes. Sebastian in particular loves helping new arrangers.
Whats all the protocol stuff I will have to do?
Finale files with ALL the correct formatting, along with a PDF and midi. I cannot stress the importance of formatting enough. If you can't do stuff with your version of finale, find the other topic in the help subforum BEFORE you submit anything.
And finally, please, please make you only submit something you are fully satisfied with. Something you wouldn't have a problem with if it was associated with you in the future.