Watch the Southern Comfort online guitar lesson by Jeff McErlain from Beginner Blues-Rock Soloing
This is a great chord progression to cut your teeth on using major pentatonic. As you can see, I've also added in some notes outside of the pentatonic scale, with these borrowed from the A Mixolydian scale. Often times the pentatonic scale is easier to use than a major scale or mode simply because we have two less notes to worry about.
We're mainly using A major pentatonic here, A B C# D F#. If we take a look at an A Mixolydian scale, A B C# D E F# G, we see that they're very similar. For now, don't worry about the idea of a Mixolydian scale, focus in on major pentatonic, keeping in mind that the two are closely related. You have plenty of time to dig into Mixolydian later!