I don’t know what your native language is, but the passage you quoted is basically it.
You wear the green scapular and pray for the conversion of someone you know. It could be anyone.
I have also heard some people place the green scapular under their non-catholic spouse’s side of the bed and pray for their spouse’s conversion that way.
I am no expert on the green scapular, only commenting on what the passage said, and what I have heard other’s say about the green scapular.
You should try and search the term “green scapular” or “scapular” on this forum to find threads and more information on these sacramentals.