You need to have the path of the other Word document and a defined range for the text you want (e.g., table cell, content control, bookmark, etc.). In your active document you need a target for the text. Something like this:

[VBA]Sub Demo()
InsertFileRange "bmTarget", "bmSource"
End Sub
Sub InsertFileRange(ByRef strBMTarget As String, strBMSource As String)
'Identify the file name and path of the data source
Const pDataFile As String = "D:\\Data Stores\\IncludeText Tip\\IncludeTextDataStore.docx"
Dim oRng As Word.Range
Dim oRngFileRangeEnd As Word.Range
'Set a target range for the text to insert. This is the bookmark "Narrative" range.
Set oRng = ActiveDocument.Bookmarks(strBMTarget).Range
Application.ScreenUpdating = False
'Clear target range of any previous content. This deletes the bookmark.
If Len(oRng.Text) > 0 Then oRng.Delete
'When you use InsertFile method you have to use a little Word trickery to determine the range of the inserted text.
'Anchor range start
oRng.Collapse wdCollapseStart
'Create a duplicate range
Set oRngFileRangeEnd = oRng.Duplicate
'Add a temporary character to the duplicate range
oRngFileRangeEnd.InsertAfter "*"
'Insert the content
oRng.InsertFile pDataFile, strBMSource 'Add ", , True" to link to the source text.
'Remove the temporary character from the duplicate range.
oRngFileRangeEnd.Characters.Last.Delete
'Anchor range end
oRng.End = oRngFileRangeEnd.End
'Re-create the bookmark
ActiveDocument.Bookmarks.Add strBMTarget, oRng
Application.ScreenUpdating = True
lbl_Exit:
Exit Sub
End Sub
[/VBA]