Permission controls

Sorry for my late response! You find the particular permissions in the "permissions" folder, either you can edit the "default.permissions", those are the basic permissions which affect all players and groups, or you can create a new group in the "groups" subfolder, or edit the existing example "admin.permissions" file. By default, the admin.permissions group already has access to the creative mode. To become a member of this group, you have to type setplayergroup playername admin into console.
If you need blueprint permissions, too, you can add these lines to the bottom of your "admin.permissions" file:

blueprints:
    use: true
    create: true

Remeber to save the file and restart the server, so your changes will take effect

Glad to hear that