STEP 3 SQUARES: Secure & Infill
It is recommended to use 16D twisted galvanized deck nails (3.5" length) or 16D galvanized finish nails and nail every turf corner 1" in from the edge or corner and every 4" to 6" along all outer edges. Careful not to drive the nails too deep (not past flush) which can leave a depression and pull on the turf. When nailing, be sure to spread the turf fibers away from the nail head so it doesn't fold over and trap any fibers.
NEXT, Infill Play Sand SLOWLY by hand. Add some sand by broadcasting onto the turf squares against the grain of fibers, then brush sand against the fiber direction until it stands up evenly and sand is dispersed and not clumped. Be careful not to be too heavy handed (too much / too fast) and bury any fibers which will create an uneven looking surface. You should be adding enough sand to fill up to just below the paver surface. Repeat this step until desired finish & firmness is achieved.
You can use a shop vac to suck up and re-use any sand and a leaf blower to help disperse any clumps and to help with clean up afterwards. Lightly spraying with water will also help to seat in the sand once completed. Rain will help this process as well. You may need to apply sand in a few applications as it settles and you may lose some material with rain over time.
CONGRATULATIONS ON A JOB WELL DONE AND YOUR BEAUTIFUL NEW PAVERTURF INSTALLATION!!!