Both may be possible, depending on context. Please post the full sentence.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Nafisi What are we supposed to do for next session?The article is optional there. Dropping it feels slightly informal to me, but that's fine in this conversational sentence.
Nafisi What are we supposed to do for the next session?Maybe it's an American thing, or maybe it's just me, but I can't imagine this one without "the", even in the most informal of settings.