I would brew and ferment the beer portion first, then add the grape concentrate after the primary fermentation finishes...then let it finish out and continue as you normally would.
Packaged: Vienna Simcoe SMaSH, Mayan Stout, Caramel Quad, Basic Spiced Cider, Spur of the Moment Graff
Recent Meads: Cherry Melomel, Belgeglin, Bochet
Primary: Fresh Simple Cyser
Secondary: Why do I keep this line here...?
Bulk Aging: Mead Day '11 Ginger Metheglin, Cocobochet, Mead Day '12 Traditional (orange blossom) Mead
Planned: Hop Metheglin #3 (NZ hops), Trad. Gesho T'ej