Perhaps some of Apple's Help articles will help you?
(1) Your HDD based DCR-SR68 can't record directly into iMovie.
Tape based camcorders can. Full info: http://support.apple.com/kb/PH2155
If your system is working properly, iMovie can import AVCHD video clips from your DCR-SR68.
(2) To import clips from your DCR-SR68, those clips
must have been recorded in AVCHD video format.
For additional important considerations, see http://support.apple.com/kb/PH2143
(3) For more info on iMovie and your HDD DCR-SR68,
see http://support.apple.com/kb/TS1059#3
(4) For more general info on getting iMovie to recognize your camcorder,
see http://support.apple.com/kb/PH2146
Mac OSX 10.8.2