"Together we look at the boys."
Translation:Ni kune rigardas la knabojn.
"Rigardi" is a transitive verb, unlike "to look at" in English. A close analog in English would be the verb "to regard".
So you can think of it like "Together we regard the boys", where "boys" is a direct object.
But the equivalent and more natural sounding sentence is "Together we look at the boys".