Step One: Press the "Print Screen" button located on the top right hand corner of your Keyboard, (Alot of laptops require you to hold down the "FN" key then press Print screen)
Step Two: Open up Paint. Press Edit, And click paste. The picture of your entire screen should appear.
Now Choose the Box tool, And Square off the area you wish to post.
Right click inside that box and copy it. Then click the paintbrush tool, go to image at the top and click clear.
Don't freak out, Your picture should still be saved, only now only the area you want is saved, So go to edit again and click paste.
Click the Paintbrush tool once again and scroll both scrollbars so that you see a blue dot in the bottom right hand corner, Drag that blue dot to line up with your picture. then save it.
Step Three: upload the saved picture to Imageshack, Or Photobucket if you have an account and paste the Image code.