I have no problems uploading pictures from Photos to my Wordpress blogs or Facebook. I haven't used a Windows pc for over five years but don't remember it being much different. Remember the Ctrl key in Windows is Cmd in Mac.
Wordpress - in a new post:
click on Add Media
> Add new
> scroll down under Photos until you reach the album you want
> click on your image (hold down Cmd key if you want multiple images - it would be Ctrl key in Windows)
Your images go into the wordpress library
Facebook
From Facebook, pull the images the same way - in the post, click on the camera in or Add Photos and scroll down under Photos until you reach the album you want. Proceed the same as for Wordpress.
You can upload pictures straight from Photos by clicking on the up arrow at the top of the screen buty you must connect your facebook account to the Mac first.
Maybe it would be a good idea to go to your Apple Store and sign up for some of their free tutorials.