Now that you know the 12-bar blues has nothing to do with alcoholism or depression, it's time to learn how to play the second measure. You're still working on a 4/4 time signature, so each quarter measure is a single beat. However, the second measure is played in a D chord, as opposed to the A of the first.
This video will show you how to play the second measure and once again uses Elvis Presley's version of "Hound Dog" to demonstrate proper usage and technique. But you're not done yet. Learn how to play the third and final measure of the 12-bar blues by watching the video on the next page.