Install a flagpole by digging a hole the size the pole manufacturer recommends, centering the ground tube in the hole and making sure it is plumb. Pour concrete in the hole surrounding the tube. Allow at least three days for the concrete to set before proceeding with the installation.
Prior to beginning the project, check with local building codes to ensure it is compliant with regulations. Call the underground utilities locator service to ensure there are no buried lines in the area where you are digging the hole. If necessary, relocate the pole to a safe location.
Once the concrete cures, gather several people to help with the erection of the pole and discuss the directions with all members. Assemble the flagpole per the manufacturer's directions. Station one person at the end of the pole over the hole who keeps the pole centered and pressed down so it falls into the hole once it is upright.
Drive four wedges into the space between the pole and the underground tube to hold it in place. Pour six inches of sand into the void between the pole and the underground tube. Tamp the sand into place and check to ensure the pole remains plumb. Continue adding sand and checking the pole every six inches. Stop adding sand when the level reaches two inches from the top. Fill the remaining void with tar or silicone.