What version of Premiere Elements Mac are you using and what are your camera settings that you are recording at? Are you in a NTSC or PAL area?
I have premiere elements 10
I am in PAL area
Camera settings are FXP (17mbps)
As a first pass at this I would transfer the video from the camera to the computer hard drive and from there import that into Premiere Elements 10 Mac with Premiere Elements 10 Mac Get Media/Files and Folder. Under the circumstances your Premiere Elements 10 will perform as a 32 bit application running in the 32 bit compatibility mode of the Mac 64 bit with the limitations of 32 bit. I am an Elements Windows user, but the principles and suggestions that I am about to make should be applicable to your situation. I have gone off track with any Mac specific details be sure to say so. The 32 bit business means that Premiere Elements 10 Mac will not be able to take advantage of all the 64 bit resources as would be the case if you had Premiere Elements 11 Mac running in a Mac 64 bit operating system.
Your Canon HF-R18 FXP would be highest quality 1920 x 1080 with a bitrate of 17 Mbps (megabits per second). I need to confirm if you are recording interlaced video 1920 x 1080 (50i) or 1920 x 1080 p25 (in the progressive mode). From what I have read your audio is Dolby Digital Stereo.
If 1920 x 1080 (50i, aka 25 interlaced frames per second), then use the Premiere Elements 10 project preset = PAL/AVCHD/Full HD1080i25.
If 1920 x 1080 (25p, 25 progressive frames per second), then use the Premiere Elements 10 project preset = PAL/DSLR/1080p/DSLR 1080p25.
In either circumstance, when you drag the file from the Media area to the Timeline, do you see a colored line over that content on the Timeline? You should not be seeing a colored line over this content if we have the correct project preset selected. But remember that, each time after you edit that video, it is normal for a red line to appear over it. That is the program telling you that you need to render the Timeline content, one way by pressing the Enter key of the computer main keyboard to get the best possible preview. When the rendering is complete, the red line will turn green. Thereafter, only a red/green indicator system (with all its implications) will exist for letting you know if the program thinks that you are seeing the best possible preview. No more non colored line choice, just red (need) and green (not needed). When you are in the no colored line or green situation, pressing the Enter key will just get you playback of the file in the monitor - no rendering available.
See what that looks like on the Timeline at playback there.
Let us start there and be ready for the next phase "How do I want to export that Timeline?" with all the details associated with that phase to get the best results.
Looking forward to your follow up.