The remote release has a button and a slide switch. Slide the switch to move the mirror up, then press the button.
The remote release came in the camera package with the body, 80mm lens, charger and strap.
The camera didn't come with a remote (used), so I was hoping to get a replacement for it from a third party. I use a Canon remote to trigger my Bronica, but it's only a single plug (unlike the Rollei).
as far as i know, you will need the rollei electronic release.
one place you might try is the medium format camera section on eBay - specifically the rolleiflex listings - where they show up from time-to-time. you might try keh camera as well.
i might have an extra at home...out on the road now, but will check when i get back.