Sony NX3 is taking a wedding in the hotel, and the lights are flickering. How to shoot? I can't see my face clearly! How to set it?

When shooting the newlyweds in the hotel, the lights of the hotel are flickering. At this time, the hotel lighting can not be used as the main light, as the basis of exposure, we should turn on the flash and use the flash as the main light for correct exposure. However, because the autofocus file is difficult to focus, it is necessary to focus by manually observing the distance. I can't see my face clearly when taking pictures, and there is no way to do this. Unless there are other lighting equipment, you can only see the outline of the new person.