Quick way of the top of my head... you'll need the Group ID first, so assuming you have the Group Name, use the Get Group By Name component to fetch the Group ID.
With the Group ID, call the Get Users In group component, passing the Group ID is input. This returns a string array of all user emails in that group.
Once you have the result array, loop through it using a For Each Element In Collection and use a Send email to send the email.
Another option is to just use a distribuion group email address (if one is set up) for a particular group.
Hope this helps.