There are many ways to do that. You can simply copy the link from the address bar and send it, or send the List-Number displayed to the left of the list name. You can use the Share function (bar above the list, Share icon) to send an email to all participants. If you use the app, the Share icon starts the familiar Share function of your smartphone/tablet. Alternatively, you can print the list (toolbar above the list). On the printout you will find the link to the list, the List-Number and even a QR code to scan.