I'm very new to Kdenlive, and I want to import some .mts video taken from my camera. So, I click on the button to import clips, select my file, and click "Okay", nothing happens. Nothing shows up, nothing changes. I'm not really sure what to do or try.

You'll need to provide more info. What version of kdenlive, how was it installed, just the basics.

Yeah, I thought so, I just didn't know what to include.

Version: 0.9
Installed through: Apt, at the ppa.

Let me know if you need ay more information.

Have you tried to copy the MTS file to your home-folder first, and then add the clip into kdenlive from your home-folder?

Otherwise it could be MLT in your system that can't open the MTS file. I'm only guessing. Might help to build kdenlive from the build script, but it's a bit more tricky that installing from apt-get ;)
(had to put in a extra space due to the spam filter): www.kdenlive.org/forum/ build-script-instructions-new/