It seems that I have often found topics that are almost similar to this, but I will still try to answer.
for beginners you should choose exchanges with high trading volumes such as binance, bittrex etc.
You only need to register in the exchange, but there are several exchanges that require KYC.
The trade you have to do is buy low and sell high, but you should never consider this easy because everything is not as easy as imagined. in trading you have to do a lot of research and don't be easily influenced by others and the main thing is to be able to control your emotions.