Attach your camcorder to your Mac via USB. Make sure camcorder is plugged in to AC power (not batteries only).
Open iMovie. The import screen should appear. If it does not after a minute or two, click FILE/IMPORT FROM CAMERA.
On the import screen, toward the bottom, you should see a button that says "Create Camera Archive". Click this button to make an identical copy of the files on your camera. Onve you have this, you can import into events so you can edit by using FILE/IMPORT/FROM CAMERA ARCHIVE.
More at this link.
I did that and all the video files saved as MTS files (almost 800 of them) and I have to use a ripping software to make them usable for IMovie. That would not be a problem if there were not so many of them. I did not see an option when I chose "Create Camera Archive" to determine what kind of file it is saved as. It seems like it should be easier than this. I backed it up multiple times saving in different areas (Mac hard drive, external hard drive) and it comes out the same way each time.