I need help setting up PEX permissions.yml

Hi i am making a Percy Jackson server which is based on the book. Whenever i go onto the server and i type /pex, it doesn't show anything. Is it better to just create the groups on the console by typing /pex group [groupname] create, or is it just easier to do it on permissions.yml?

Anyways, here's my template

Code:

groups:
  Unclaimed:
    default: true
    prefix: '&e(Unclaimed)&e '
    build: false
    permissions:
    - essentials.help
    - essentials.rules
    - essentials.motd
    - modifyworld.chat
  Aphrodite:
    default: false
    prefix: '&d(Aphrodite)&f '
    build: true
    permissions:
    - essentials.help
    - essentials.rules
    - essentials.motd
    - essentials.afk
    - essentials.help
    - essentials.home
    - essentials.mail
    - essentials.mail.send
    - essentials.me
    - essentials.motd
    - essentials.msg
    - essentials.ping
    - essentials.rules
    - essentials.sethome
    - essentials.spawn
    - essentials.suicide
    - essentials.tpa
    - essentials.tpaccept
    - essentials.tpahere
    - essentials.tpdeny
    - essentials.warp

...And so on with the same inheritance for the other groups.
Anyways, can someone help me?? I have over 10 groups and i only posted the 2 groups on here or it would've filled up the page.