How do I get that instant radiance?

I bought Boots No7 Instant Radiance lotion and it says use alone or under foundation. Could you tell me if and when I should use a moisturiser, because the girl in boots didn't seem to have a clue!

Chocolate meringue with rose chantilly

Spoon the mixture on to the paper circles, taking it almost to the edge and lightly swirling the top. Place in the oven, ...