If a video clip from that camcorder is the first clip on your timeline, the program will do its best to match the video specs.
If you can't match the video specs, you can try to set it up manually by starting a new project. On the New Project panel, click Change Settings and, on the Change Settings screen, select NTSC/AVCHD with the AVCHD 1080p60 option.
I don't believe there is a 5.1 audio option for this video setting, however.
I have a Panasonic SDT750 camera and am still on PrE 13. I have no trouble retaining the 60p from the camera, but have never been able to use the 5.1 audio. I use the standard technique (that Steve suggested) of sliding a key clip to the timeline to start the project. At output, there is a sequence of choices where you can "match source" and create MP4 files that are very close to the original files.
My Panasonic camera came with Panasonic's HDWriter software. It is clunky, but will retain the 5.1. It is clunky enough that I've abandon using it in favor of the much better PrE.
FWIW, the 5.1 sound on the Panasonic camcorders comes from mics clustered tightly together in a small spot on the camera. So the camera may be recording 5.1 tracks, but without appropriate mic placement, those tracks are not really very useful. Even in the stereo mode, there is little left-right separation.
Thanks for the responses. I also have tried changing the project settings, but haven't found a way (using Adobe Premiere Elements 14.1, trial version, on a Mac) to retain the combination of 1080p 60 fps and 5.1 audio features of my clips.
I've found that if I edit these clips on my Mac using Apple's iMovie (v10.1.2), the 1080p 60fps feature of the Panasonic clips is retained, and the "stereo audio" that iMovie creates apparently contains encoded surround sound (Dolby ProLogic?). When played through my stereo, the surround sound of the final iMovie-generated movie seems comparable to the (very good) 5.1 sound of the original clips.
So, for now at least, I plan to use iMovie rather than Premiere Elements for my video editing.