www.atlantahoops.com > In-Ground Basketball Goals
The Spalding 88369 NBA Inground Basketball Goal System includes a 60'W x 36'H Pro style extruded aluminum framed Tempered Glass or Acrylic backboard ... Click here to download the Spalding 88369 Basketball Goal Owner's Manual
https://www.spalding.com/Possible instructions but registration required to find out if it still exists.http://pfd.cloudz.pw/download?file=spalding+44+77537t+assembly+instructions
Dig below frost line, depends upon where you live, but at least two feet deep. I would make the hole about a foot wide. Pole diameter 3-4 inches in diameter.