I'm relatively new to the crypto world as well, but if I'm not mistaken, you'll have to wait for the Developers of those tokens/coins to list their coin on the various exchanges. Usually, there is a 'fee' to be paid to these exchanges to list. Members of the exchange can 'vote' or 'suggest' that a coin be listed as well.

Once it is listed, then you can trade it for BTC or cash or some other coins.