How do you do direct and indirect object pronouns in Spanish?

I can't really get it... I dono if someone can explain it or send me a link or something... I just gotta know how to do it for my final tomorrow.How do you do direct and indirect object pronouns in Spanish?
A Direct object pronoun consists of lo, la, los, and las.





E.G.: I buy meat.


Yo compro la carne





Yo la compro.





E.G.: I invite my friends.


Yo invito mis amigos





Yo los invito.





Indirect consists of le and les





E.G: I see her.





Yo le veo





E.G.: I see them





Yo les veo.