In case of the token has not been list exchange. Use Forkdelta (Etherdelta). Decentralized exchange, buyers, and sellers exchange themselves.
You must manually add token contract address (If it has not been added yet), then set the price to sell.
If anyone interested in token that you are selling, they will seek.
If it listed any exchange (Okex, Kucoin, Hitbtc, Idax, Idex ...) you just need to create an account at exchange, deposit token and sell.