He should have Googled it:
https://legalbeagle.com/6140153-file-mechanics-lien-louisiana.html
The procedure is relatively straightforward.
I’ve had a mechanics lein on an a/c company for 10 years or so, the guy clearly ripped me off, sold me a high seer unit when I filed my taxes and tried to claim the tax benefit, I found he put a less efficient unit in and did not qualify for rebate. I was told I would receive my money at some point, I heard recently the guy died, I haven’t seen any Money. Big waste of time and effort.