1) are your tack strips in good condition? If not, install new ones all around the perimeter of the room.
2) Install new pad or use existing pad. Many new carpets have specs for pads, check out yours.
3) Rent two knee pad carpet kickers. One for each helper.
4) Tools needed, kickers, box knife with plenty of sharp hooked blades, putty knife, hammer, tack strips, new thresholds.
5) Start on the 28 foot side and secure the carpet all the way down the side. Make sure that the carpet ends are down over the tack strip and under the molding, Use the putty knife to push the carpet down between the tack strip and the molding.
6) Go to the other side of the 28 foot wall and begin using the stretcher to tightly secure the ends to the tack strip. You might have to make several passes.
7) Before you securely attach the entire section jump to the sides and pull on them so that you are not creating any waves. do the same on the other 15 foot side. You will jump back and forth on the sides and other long side so that you are not over stretching the long sides to the extent that stretching the short sides are creating waves.
8) go along that 28 foot wall again re stretching until it is taunt. Cut off any excess from the side where kicker is used. push excess in crack.