For a day make-up the main aim of the base is to give the skin an even appearance.
Squeeze a little foundation out of the tube onto a clean spatula. Work from the spatula using a clean, dry latex sponge or a slightly moist make-up sponge, applying the foundation to the skin in a thin layer.
If you want a more transparent but still mat result, you can mix the Foundation on the spatula with Under Make-up Base.