The background behind the guests is very dark. Which settings help?

Use the camera’s manual mode (M). Proven starting values: a relatively high ISO, aperture opened to around f/5.6, shutter speed around 1/80 second. Then reduce the power of the studio flash until the people are correctly exposed.

The longer shutter speed and higher ISO let the camera capture more ambient light, so the room behind the guests becomes brighter while the flash only lights the people. Check the result with a few test shots at the venue, as every room is lit differently. The cameras that work with the software are listed on the camera page.