use some good quality spray glue from Home Depot or Lowes. And spray both the box and backing of the carpet, wait like 30 seconds then wrap it. role the front/top/back/bottom make your seam on the bottom. then when u get to the side it gets a little tricky, if you want all of your seems to disappear. haha
its had to explain but cut up from each corner so u have 4 flaps and fold them in and where ever one meets another. lay them on top of each other and cut through both then pull them up and take the scraps away and your edges should match up nicely. Idk how easy that is to understand. look up some youtube vids on how to do it if its too confusing. ha