How do you buy crowns on steam?

Hello there, could you please elaborate on the process of purchasing crowns on Steam? As someone who's interested in expanding my gaming experience, I'm curious about the steps I need to take to acquire these crowns and use them in-game. Are there any specific requirements or limitations I should be aware of? Additionally, could you share any tips or tricks that might make the purchasing process smoother? I'd appreciate any insights you could provide. Thank you in advance!