First, make sure that your computer detects your camera when you connect it – you may need to install a driver. You should also be able to see the camera as a removable disk drive in Windows Explorer.
If you have Movie Studio Platinum, you can try using its built-in Device Explorer (on the View menu) to import camera footage directly from the camera over its USB port. It should automatically detect the camera and give you a list of clips to import.
The other option is using Panasonic’s software to do the import. You should have received a software disk with the camera. I don’t know what the prosumer/pro cameras come with, but consumer Panasonic cameras come with something called HD Writer which doubles as a capture/import utility and basic editor/converter. It will copy the AVCHD footage from the camera and give the files sensible time-stamped names, and you can then use them directly in Vegas.