This just creates a new note in notes.app. To keep it simple, it just uses the first folder in the first account it finds. You can change this behaviour by editing providing the respective names in the "properties" in the applescript.
To search existing notes, type "n search_term" into Alfred. E.g. "n something I wrote yesterday" (not working in macOS High Sierra)
To create a new note, just type "n note_text" into Alfred. E.g. "n something very important I will