Using word ( stuffing) to refer to information, speech

Yes, this sentence is grammatically correct. It is a metaphor. "Stuffing" normally refers to filling a space as full as possible or overfilling something. In this case, the question means that the speaker wants the listener to add the information into chapter one, even though chapter one is already complete in some way (which is like being full), so adding more information is like overfilling it.

“Stuffing” information into a chapter is extremely informal, suggesting the information isn’t really worthwhile or may not fit there.

You could suggest adding the information, combining it with chapter one, or integrating it with chapter one.