1. First you need myetherwallet to receive token
2. You need to know where the token is listed, you can find out at their telegram or website.
3. Send them to exchanger then sell them. You able to choose to be ETH, BTC as long the exchanger support the exchange.
4. Keep them on your cold wallet, don't keep them in your exchanger wallet.
In order to transfer your ERC20 bounty tokens from your wallet to an exchange, first you'll need to have enough ETH for that transaction.