How do I make adjectives agree in French?

Adjectives are words used to describe something for example blue, funny, nice
To make adjectives agree in French, first you need to look at the subject (the person or thing thing the adjective describes) and see whether it is masculine or feminine. If the subject is masculine then the adjective stays the same but if it is feminine add an e to the adjective. For example, for the adjective 'grand'(big) in the sentence John est grand. (John is big) - John is masculine so the adjective stays the same. However for the sentence Emma est grande (Emma is big) Emma is feminine so you add an extra e.
Next you need to look at how many people or things is the adjective is describing. If there is more than one masculine subject doing the action then you add an S to the adjective and if it is more than one feminine subject add es. For example 'John et Paul sont grands' (John and Paul are big). John and Paul are both masculine so you add an s. However for the sentence: 'Emma and Jane sont grandes', (Emma and Jane are big) you add an es as Emma and Jane are feminine. If there are both masculine and feminine subjects you just add a s. For example Emma, Jane, John and Paul sont grands. (Emma, Jane, John and Paul are big) there are feminine (Emma and Jane) and masculine (John and Paul) subjects so you add a s.