There are a few ways to get a HUD.
NOTE: It is strongly recommended you add the SL Experience “Permissions Request” to your parcel, otherwise each part will have a manual attachment permission, and teleport functions can not work. To add the experience, go to your parcel details window, on the last tab “Experiences” press “Add” next to “Allowed Experiences”, search for “Permissions Request”, owned by “Iain Maltz” and add that to your parcel.
Primarily, when you first get a GPHUD server, the only way to get a HUD is by clicking on the GPHUD region server its self, which will trigger a hud attachment process. This is not expected to be how you use it day-to-day, just how the product ships to avoid intruding on anyone.
You can either use an “on click” dispenser (or multiple dispensers) - to set this up, either stand near the server and issue “*instance.getDispenser” or with a HUD on say “/1instance.getDispenser”, a script will be sent to you. Place this script inside whatever object you want the user to have to click on to get a HUD sent.
There is also the often preferred AutoAttach method (you can use this /and/ dispensers if you really want), this will automatically prompt new visitors to the sim to accept the experience and then attach a HUD, if they have accepted the experience previously the HUD will simply automatically attach to users when they land on your sim (and disappear when they leave) with no user interaction being necessary! This can be configured under Configuration → GPHUDServer, set AutoAttach to TRUE to enable this feature, and ParcelONLY to true if you only want the one parcel to be monitored for new visitors (otherwise it will monitor the whole region if left with the default FALSE setting).