How do I convert my core to USDT?

Could you please explain to me how I can convert my CORE tokens into USDT? I'm not entirely sure of the process and would appreciate a step-by-step guide. Should I use a specific exchange platform? Are there any fees associated with the conversion? Also, is there a specific time of day or market conditions that would be more favorable for making this conversion? It would be great if you could provide some insights on these matters. Thank you in advance for your assistance.