Doubt many here have used it.
(And for those who don't know what it is, I too had to look it up - It's a donation module for Gmod, allows donations for various stuff/credit/access)
As you didn't give any detail, as to your trouble or challenge, perhaps a little google-Fu would be in order?
To even learn what it was, I had to use google (meaning, I'd recommend starting with better post information in the future, at any forum, not just ours)
Using Google "Gmod prometheus", the first link came to a page that said this
Please use this for support and not ScriptFodder
https://nmscripts.com/prometheus
Steam group: http://steamcommunity.com/groups/PrometheusIPN
The second link was a youtube video aptly named "Prometheus: A Gmod Donation Module Installation Tutorial "
