Remove the wooden trim around the walls. Find the midpoint of the area with a chalk line drawn from one corner to the opposite corner of the room. Mark the center with a large "X" using two perpendicular lines. The room is now divided into four quadrants.
Prepare the subfloor by removing debris and vacuuming the area. If cracks are present in the concrete, use a concrete sealant to fill in the spaces.
Install the first square of carpet along the "X" in the center of the room. Lay carpet squares adjacent to one another until you reach the walls on all sides of the room.
Cut excess carpet using a row cutter or utility knife if you reach the wall and it doesn't fit. Create a small slit where you want to begin your cut. Then, remove the carpet and cut a line down the back starting from the slit to ensure a clean cut with no fraying.
Fill in gaps around the base of the walls with cut squares. Align the factory edges of the carpet tile together with the carpet square nearest to the wall for a clean fit. Trim the edge of the carpet closest to the wall leaving room to add the trim.
Set the trim back in place around the base of the wall using a staple gun or set of nails.