How do I buy and sell crypto on OKX?

Excuse me, I'm new to the cryptocurrency world and I'm interested in using OKX for buying and selling crypto. Could you please explain the process to me? I'd like to know how to create an account on OKX, deposit funds, choose which cryptocurrencies to buy, execute the trades, and then withdraw my profits if I decide to sell. Could you also tell me if there are any fees involved and what security measures OKX takes to protect its users? Thank you very much for your help.