Okay, since there are a bunch of newfags on here and I myself was a newfag a mere two hours before writing this, I have made this copypasta to get you started on cryptocurrency trading so that newfags can stop asking in the board. I will also explain how trading works in Bittrex.
1) Have a debit or credit card.
2) Go to coinbase.com and make an account.
3) Go under "Buy/Sell" and buy Bitcoin using your money (not Ethereum or Litecoin. Those won't work for the next part unless you use a trading site that specifically uses ETH or LTC).
4) Go to Bittrex or Poloniex (Poloniex isn't legal in my state) and make an account (from this point on I'm assuming you're using Bittrex).
5) Open your bitcoin wallet and press the blue plus sign next to it. It will prompt you to get your wallet code. After you are shown your wallet code copy it. Go to Coinbase and go under "Send/Request". Paste your code into the address field and then select the amount of Bitcoin you want to send over (I'm assuming all).
6) Wait until the transaction is confirmed. This should take about twenty minutes (no, you didn't lose all your money).
You are now ready to begin trading altcoins. Have fun getting to the moon. And remember, there's a fee pretty much anytime you want to move your coins, whether you're buying bitcoin from coinbase, moving your bitcoin from coinbase to bittrex, or buying/selling altcoins on bittrex.
Now find a coin you want to trade.
Say Digibyte. bittrex.com
Scroll down. See "BUY DIGIBYTE" and "SELL DIGIBYTE" under "TRADING"?
"Units" is how many units of altcoin you want to buy. Put 100 in here if you want to buy 100 DGB. Put 18710.3518 if you want to buy 18710.3518 DGB.
"Bid" is how much you want to pay per DGB. meaning if you put 100 in Units and .000005 in Bid, you're going to spend .0005 in Bitcoin for 100 Digibyte (a little bit more actually, because of fees.
You can click those blue tabs under buy/sell to accept offers.