I see in the configuration file where it has the certain default blueprints you want unlocked, but I don't see anywhere in the description where it tells you what to put in that area. Am I missing something?
Merged post..

Nevermind I finally figured it out. I just tried...

{
"Settings": {
"Default blueprints": [
"rifle.ak"
]
}
}

and it worked. :P

HOW!? lol this isnt working for me lol

Likewise, it's not working for me either.

Merged post

I examined the code, and this depends on having a particular permission "blueprintmanager.config" or "blueprintmanager.all". Whatever is in the config file will apply for anyone with the first permission. Presumably, anyone with the second permission will get everything. I only tested the first perm.

Yeah. blueprintmanager.config -- Grants access to all blueprints specified in the configuration file You don't want to grant .all. 

Try disconnecting and reconnecting and see if that works.