Why can't you post pictures that you took on your Asus c300 chromebook to facebook?
You can upload pictures to Facebook through your Chromebook. If
your pictures are saved in the Chromebook's SSD, Facebook should be
able to recognize the drive and you can upload it from there. If
your pictures are saved in the cloud (ex: Google Photos), you can
download the photos to the Chromebook's SSD, turn around and upload
it from there to Facebook (note: Google Photos on the desktop
doesn't allow for sharing to Facebook directly, but does allow it
on a mobile device).