Hello there.

Welcome to CreateBlog. I'm Sarah and if you've any questions about any other stuff on the forum, don't hesitate to ask.

To answer your question..
-If you have a PC: Press the PrintScreen button on your kebyoard, it should be at the top inbetween the number pad and the letter keys.
-If you have a MAC: Shift+Ctrl+3 for a full screenshot, or press Shift+Ctrl+4 for a select screenshot.

And unless you do the select screenshot (Mac), just go to an image editing application and paste your screenshot into a new document, then crop out whatever you don't want to show in your screenshot.
Hope that helps, and I also hope to see you around.
Have fun posting.