Sweep the top of the concrete slab clear of all debris.
Open your liquid vapor barrier product and pour it into a roller paint tray just as you would pour regular paint into the tray.
Place a new fine foam roller pad over your paint roller by pushing it onto the roller frame (the roller pads are made on hollow tubes that slide over the roller frame).
Roll the paint roller into the liquid vapor barrier in the paint tray so the entire pad is covered. Roll the roller pad on the high sloped part of the tray (with the molded ribs) to spread the liquid vapor barrier evenly throughout the foam of the roller pad.
Apply the liquid vapor barrier to the concrete slab. Work from one corner out to the edge of the slab making sure that you apply the barrier evenly and that you do not miss any spots. Wait 5 to 6 hours for the barrier to dry and then apply another coat and let dry for 12 hours. The final coat needs longer to dry because it is not being absorbed into the concrete but sitting on top of the prior barrier coating.