If I wanted to become a vendor at an event how would I do that and who would I contact?

Usually the arena isn't the employer of vendors. Example: Pittsburgh sports has had Aramark vendors, in which case, you'd be applying through them.

I believe Aramark is the vendor at Nationwide Arena. Check out the Aramark website fir employment.

If you have some special product you want to sell you might contact them directly but if you just want to work during events check their website.