1. If the noun is feminine, the word for THE in Italian is LA

Therefore, to say THE FROG you simply say, LA RANA

2. In Italian the word "IS" is "È"

3. If the noun is feminine, then the ending of the adjective changes to an "A" from an "O" to agree with the word.
Therefore, THE FROG IS QUICK is LA RANA È RAPIDA