This camera does not have built in wifi so you have to first transfer the pictures to another device (computer, iphone, iPad) to be able to send it to Facebook. I'm told (but haven't checked) that the newer model, the SX280 HS, does have built in wifi. I don't know whether that would direct posting to Facebook but would hope that this is a function. You might want to check the Canon site if you're thinking of the 280 for that purpose.
There may be other ways to do it, but this is how I post to fb. Download pictures to my computer. Go on to fb select download/create album. You have to know where you saved the pictures, fb will give you prompt to browse and you go to where you saved the pictures. You then select the pictures you want and "open" them, they will upload to fb.