1. Go to the admin page, 2. Give the shortcode name as "test" 3. Enter the content as, "THIS IS A TESTING SHORTCODE" and click create shortcode. 4. Go to the post edit page, enter the code [sc:test] and publish it. 5. In the post you should see "THIS IS A TESTING SHORTCODE" in the place where you typed the code [sc:test].
Doesn't this work for you ??? If yes please post the screenshot of the page.