How do I add this into my textbox?

[makai]

Text1.SelStart is the location of the cursor

so you use

Dim S$, where&
S = Text1
where = Text1.SelStart

Text1 = Left$(S, where) & _
        "your text goes here" & _
        Right$(S, Len(S) - where)

put in
& vbCrLf &
where you want your text to start on a new line