Taking screenshot and sharing them online is really easy.
To take screenshot (print screen) you simply have to press:

Ctrl + Shift + P

To press that combination is easy, you just have to keep the index finger on the shift, middle finger on Ctrl and the right thumb on P (or which ever way you are comfortable with using the combination).

You can go to the photos from the application and see them there. Add tags, choose share and choose the service you want (like Flickr).