Endings must be attached to stems in order to decline a noun. To find the stem of any noun, go to the genitive case and remove the ending. This is your stem. Like puella, puellae–the girl. The stem is puell.
English 1. The girl sees the poet. 2. The poet praises the girl’s beauty. 3. The poet gives the rose to the girl. 4. The poet loves the girl. 5. The poet makes mistakes without the girl. 6. O Girl, I love you! Latin 1. Puella poetam videt. 2. Poeta formam puellae laudat. 3. Poeta rosam puellae dat. 4. Poeta puellam amat. 5. Poeta sine puellā errat. 6. O puella, Amo te!
The purpose of adjectives is to modify nouns. In Latin, adjectives need to modify nouns in gender, number, and case. That does not mean that the endings will be the same. For example, since agricola is masculine, the great farmer has to be agricola magnus. It will become important to remember that the endings may not match.