It’s literally all on the main post. It also says that you need to check the java file if they nodes are outdated:
https://github.com/MinecraftPortCentral/GriefPrevention/blob/master/src/me/ryanhamshire/griefprevention/GPPermissions.java
Also I am not sure but I think you need:
griefprevention.admin.claim.set-admin-flags