Hi,
as you can read here there is not support for H264 with the freeware version (ivsEdits LE) . You can use some free third party applications to convert your h264 files to DV/DVCPRO/MJPEG codec. I can recommend MPEG STREAMCLIP (http://www.squared5.com/) or X-media Recode. MPEG STREAMCLIP could require a commercial PLUGIN from Apple to decode M2T and M2TS files.
Roberto Castellano