Fully covered in Photoshop for Nonlinear Eaditors (several pages long)
here is condensed.
Build your graphic in PS
Save off your background
Turn off all Layers exceopt those belonging to your alpha matte
Make new Layer
Select New layer
Hold down Option Key
Choose Merge Visible
Lock transparency
Fill with White
Make New layer underneath
Fill with Black
Merge layers
save off
Invert so black on white
Save that off too (can’t remember from top of head if DVDSP prefers w/on b or b/on w)
Bring that into DVDSP
read online help about using a highlight matte