Start with this short video to see how contracts translate into trick targets, and how to judge what level to aim for.
Here are some hands for you to try picking a contract and playing in it. The links will take you to a hand on the BridgeTraining website, where you will be able to see information about your partner’s hand on the left side - the distribution of cards between the suits, and high card points. Use this information to pick a target contract and select that from the panel on the right.