Remove furniture around your carpet seam area. Vacuum the area, so you do not get dirt and debris on your subflooring while repairing the seams.
Lift up the seams. It may be easier to have a friend hold one side of the carpet while you inspect the seams to see if they have been frayed.
Lay double-sided seam tape on the floor where both sides of the seam meet. Press an iron on the seam tape to activate the adhesive.
Apply seam adhesive to both seams. Butt the seams together and lay them on top of the seam tape. Roll a carpet roller over the top of the seams to firmly attach both sides.
Wait 24 hours for the adhesive to attach to the carpet before using the room or vacuuming.