First, let’s get our terminology straight: If you are the dealer, or the if the other players before you have passed, you get to make the opening bid. If your opponents have bid first, then you are said to be making an overcall, and if your partner has already bid you are responding.
The panel above will help you to choose the best bid if you have enough points to open at the one level (12+ hcp) and you have a balanced hand. If you discover from the panel that you hand isn’t a balanced shape you can find the unbalanced hand openings page here
If you don’t have 12+ points you might still be able to open the bidding if your hand is very distributional. With weaker hands that have longs suits you can make higher-level opening bids to try to make life difficult for your opponents (see pre-emptive opening bids)
Watch this fun video about choosing an opening bid and try the quiz here