Clitic Pronouns

Credo in te!
In English, I becomes me after words like for, in, and with. Italian does the same thing.

Io becomes me, and tu becomes te after short words like per, in, or con.
Mio padre gioca con me.
My father plays with me.
Credo in te.
I believe in you.
Lui, lei, noi, voi, and loro don't change after these short words.
È per noi.
It is for us.​
È per lui.
It is for him.
Li mangio!
To avoid repeating the same word over and over again, in English we use words like it and them. For example, I like that shirt. I want it! or Do you like these shoes? I want them!
In Italian, you can use lo, la, li, or le for the same reason. You will need to pick the one that matches your noun. Is the noun you want to replace masculine or feminine? Is it singular or plural?
I miei fratelli lo amano molto.
My brothers love him a lot.
Mia sorella la conosce.
My sister knows her.
Io li mangio.
I eat them.
Le chiamiamo al telefono.
We call them on the telephone.
Notice how lo, la, li, and le come before the verb.
Mi piace il pane, però io non lo mangio.
I like bread, but I do not eat it.
I see ya
In English, we say I see you, I see him, I see them, etc. In Italian, there are two different options:

Io vedo te, io vedo lui, io vedo loro, etc.

Io ti vedo, io lo vedo, io li vedo, etc.
So you'll use different short words depending on whether you want to place them before or after the verb. Generally, it's more common to place these short words before the verb. But it's up to you!
Lei mi offre la sua automobile.
She offers me her car.
Loro pagano me.
They pay me.
Lui ci legge un libro.
He reads us a book.
Io vi amo.
I love you all.
Le mucche ci danno del buon latte.
The cows give us some good milk.