You can use the Forget option under the Cards menu (or the menu shown when right-clicking on a card) in the card browser.
I don’t recommend doing that for all cards, as the main idea of Anki is its spaced repetition system that takes care of scheduling your study for you. See: Anki's not showing me all my cards! - Frequently Asked Questions
You can also use filtered decks, which may be a better option. See Filtered Decks - Anki Manual