I think it depends on the exchange.   My favorite exchange is Binance...but this is because they list the tokens or coins in bitcoin and in U.S.Dollars.   This makes it easier for me to figure out the actual price of something because I do not think in Bitcoin yet and have to use a calculator for each transaction.   So, Binance is the easiest but it only trades in bitcoin, ethereum, binance coin and tether.   But for buying and selling once you have bitcoin in the wallet...it is by far the easiest for a newbie.  Yobit is one place you Can trade with a few different types of tokens or coins.  

So as the previous, writer said, find the exchange that lists your token and open an account.  then use the receive token on the exchange account get the address and then plug that into your wallet's send bar...and the amount...and push send.   to be honest, I have only done this with Ethereum classic on Yobit...but it worked.     One other thing...Crypto can be confusing to those such as me...who are from the dinosaur dark ages...my experience is, find an action that needs to be performed...such as getting a myetherwallet,(easy to do now.)  and walk through the steps,  if you get to a point where you are frustrated, walk away and try again another day...send a small amount from one wallet to another just incase you are unsure of the process, this way if you make a mistake then you won't have lost a lot of money.  

Good luck and remember,  CRYPTO IS FLIPPIN' AWESOME!!!!!!!