Getting Gmail to flow into Mail Station

I’ve had my Synology NAS for less than a week and want to have my personal gmail email flow into mail station (Roundcube) so I can regularly back up my personal email. I can’t seem to find a tutorial on how to set that up. The prompts look simple in mail station but I used to get “fetchmail authentication failed” errors and now not even that. Attempts at finding this online have been futile. Any help is sincerely appreciated!