First you have to see if it is a head seam or a row cut seam is it a plush or a berber?
Berber is not a carpet you like to to put head seams into but it can be done with a dull flat head screw driver to find the row. you need latex to seal the edges be it a plush or berber.
Best to stretch the seam a inch or two to forgo any buckling in the seamed erea.
Rent a power stretcher and be carfull seams are delicate dont run the iron to high and dont melt the tape to much becouse if you do you may have just defeated your purpose