Lay a piece of lumber on the slab at a corner so that the outer edges of the lumber and slab are flush. Mark the slab at the inner edge of the lumber. Walk to the opposite corner and make a similar mark.
Snap a chalk line between the two marks. Repeat around the perimeter of the slab until you return to the starting mark. You now have the outline in which you will place your sill plate.
Measure the distance from the front edge of the slab to each anchor bolt. Mark the corresponding distances on your lumber and drill a hole through the board at each mark.
Lay the boards onto the slab -- between the edge and chalk line -- so that the anchor bolts fit through the holes. Screw a nut onto each bolt to secure the sill to the slab.