You've already seen how many Italian verbs can include short words that aren't there in English, like luisisiede. Infinitives do things a little differently when they combine with these short words.
Short words always go after the infinitives and not before them!
Mi ha detto di passarti il telefono.
He told me to pass you the telephone.
And notice how the verb loses its final ‑e and smooshes together with the short word.
Voglio dirgli tutto.
I want to tell him everything.
Voglio metterla in un altro posto.
I want to put it in another place.
Ce la faccio!
Sometimes Italian verbs have not just one, but two of these short words tagging along.
Non melo dai mai.
You never giveit to me.
Cela puoi vendere?
Can you sellit to us?
Keep in mind that when two short words go one after the other, the first one always ends in ‑e.
Telo offriamo noi.
We offerit to you.
Glielo
What’s the deal with glielo? Glielo is the combination of two short words together: gli or le plus lo.