If you are fitting onto an existing surface, you will require the adhesive for the perimeter of this area. However the grass weighs an average of 3kg per sqm, so you will not need to glue the whole surface.
The best way to do this will be with an adhesive cartridge. They can be used in a bead line or in a dot and dab fashion (making sure to keep at least 1inch from the edge so the glue doesn’t squirt out from the side.)
An important point to check, is that the drainage of the area is fine before fitting the grass, the grass will drain litres per minute so will need to use the natural run off.