How to buy ordinal punks?

Excuse me, I'm new to the world of digital collectibles and I'm particularly interested in ordinal punks. Could you please walk me through the process of buying them? Are there any specific platforms or marketplaces where I can find them for sale? What should I keep in mind when making a purchase? Additionally, are there any fees or taxes associated with buying ordinal punks that I should be aware of? Your guidance would be greatly appreciated.