1.You will need to create a character with the EXACT same name as your Minecraft account name (or it will not work).
2. Click your sites Guild Roster drop-down-menu and select characters.
3. You will have one of two options on this page to add a character. If you are adding the first character to the site, there will be a Manually button under Characters. If the site already has characters added to it, there will be an Add Character button.
4. Now enter your character name the exactly same way it's displayed in your Minecraft account, then click Add.
5. Now that you have created the character navigate to your profile page by clicking on your character's name.
6. Below is your characters profile page, take note of the Authorize Minecraft Account section. You will enter your Characters Authorization code on this page.
9. Go back to your characters profile page (from step 6) on Gamer Launch and enter your Authorization Code. Then click Authorize.
10. You are now Authorized! Navigate back to your Admin Menu->Minecraft->Minecraft Servers-> Edit Permission Groups. You should now see your character listed in blue. If your name is gray, that means you haven't completed the authorization or didn't add your characters name exactly as your Minecraft Account name.
11. You can now drag and drop your desired permission groups to your characters. To remove permissions from a member click the X next to the permission.
Useful Minecraft links
Plugin Installation Instructions
Setting Permission groups
GLPlugin Command for In-Game