If you want to be involved in BTC/Altcoins then you should start from Poloniex or Bittrex. The rule is pretty simple , you buy low and sell high. I'm probably making it sound easy while It's not , you should invest in ICOs and alts that have big potentials to grow like ICNs or Safecoins and not just invest randomly.
If you want to trade with only BTC and fiat then the same rule applies , It's probably a little bit difficult as you have no reputation on the forums to start trading but It's always possible to buy from third party services and HOLD for long term. I prefer this method personally.
So I would start with Poloniex or bittrex. I can't really understand about trading cause its my first time but I will try my very best in this trading. Even it's my first, I hope it will be successive. I think in first of trading like me is hard to understand it but when I will grow with it, later on I would really understand it.
Hope this simple guide can help you;
1. Open an account on the said exchanges mentioned by registering there.
2. Once you have your account and confirmed in your email, deposit any coin on your exchanges wallet ex bitcoin, or other altcoin.
3. If you have a bitcoin, you can buy any coins and then when price goes up, you can sell it. Or, if you deposited your altcoin,you can sell it at reasonable price you want.
4. You can repeat the process, Just BUY LOW and SELL High. Also as a newbie, just buy in small amount and just observed the price,if you lose its ok since its a small amount only but Don't Lose the Lesson.