This is the 3rd most frequent Indonesian word.
dengan
"With" or "by means of."
In this sentence, 'dengan' is used as an equivalent to the preposition 'with' to indicate companionship.
Saya berbicara dengan teman saya.
I am talking with my friend.
Here, 'dengan' indicates the instrument used to perform the action, equivalent to 'with' as well.
Dia menulis cerita dengan pena baru.
She writes the story with a new pen.
In this context, 'dengan' is used to provide a manner or condition under which the action is taking place, equivalent to 'by' in English.