This topic is not easy, but I think you are already using it since A1 without even knowing it. You just had not the right term for it.
Er geht zur Schule. He goes to school. –> prepositional object Sie besucht ihn. She visits him. –> object accusative Sie hilft ihm. She helps him. –> object dative
Those prepositional objects I like to call patterns. When you are learning a verb think about the following: Does this verb also need a preposition? Can it be without? Can it be both?
Example: warten –> auf etwas/jemanden (A) warten to wait for sth./smbd. –> mit etwas/jemandem (D) warten to wait with sth./smbd.
Ich warte auf dich. I wait for you. Ich warte auf den Bus. I wait for the bus. Ich warte mit dem Mittagessen bis du kommst. I wait with lunch until you come. Ich warte mit dir auf den Arzt. I wait with you for the doctor.
Watch the following videos and do the exercises, this will help you immensely to learn an important bunch of patterns (learning them one by one is the only method):