How do I know if I need to make the adjective agree with the noun in the masculine or feminine way?

In french, every noun has a "gender". House would be la maison, the determinant la indicates that the noun is "female". So if you were to use an adjective to describe this house, for example if you want to describe it as big, you would say la maison est grande. You wouldn't say grand, because that only would've been appropriate if la maison was a "masculine" word. This is why we add the e at the end of the adjective grand: because la maison is "feminine" and we have to respect and indicate this.You have to make agree every "feminine" noun with the feminine form of the adjective, and every "masculine" noun with the masculine form of the adjective. Adjectives in french have both versions. As long as you know the "gender" of the noun, you're all set! After a while, this association becomes automatic.