To shuck an oyster, you'll need an oyster knife and something to protect your hand. A glove or a doubled-over towel will do, or you can be extra safe with a metal mesh glove. Be sure to take your time and use caution to avoid injuring your hand.

Start by holding the oyster flat-side-up with the glove or towel in one hand and the oyster knife in the other.

Find the narrow point on one side of the oyster that marks the fulcrum, or hinge where the oyster shell opens and closes. With all fingers out of the way, carefully wedge the pointed end of the oyster knife between the shells.

Next, twist the knife to pry open the shell, and slide the knife along the opening between the shells.

Scrape the knife underneath the oyster to detach it from the shell, taking care not to lose any of the oyster's prized briny juices.

Reference: How to choose oysters (Cookthink)
Reference: What is an oyster knife? (Cookthink)