You are correct that trading is basically just buying low and selling high. If you want to trade BTC/EUR, then find an exchange that has that trading pair. There are also a few things to keep in mind when trading:

1) Choose a reputable exchange and don’t put all of your money on it. I never fully trust an exchange because they could get hacked or just steal your money. Or they might just run the site poorly and you could lose your money.

2) Try to always buy when the price dips and sell at a peak. The problem is that sometimes you think your selling high and the price just keeps going higher. For this reason, a lot of times I don’t buy all at once or sell all at once to leave myself some leverage.

3) Make sure that your sell is high enough to cover the fees and make a decent profit.