Hi, sorry for the long wait for a reply...
You
do not need to own an asset to trade futures for it.
Say i have tezos and i want to sell them on hitbtc, how would i do that?
You will have to ask hitbtc. I don't know anything about specific exchanges, or their policies.
I don't trade futures, I've just picked up some info over time.
Good luck, be careful, and don't trade on margin until you REALLY KNOW that YOU KNOW what you are doing.