The E7 Chord is found by first locating the 1, 3 and 5 (E, G# and B) of the E Major Scale: E F# G# A B C# D# E, and then adding a flat 7 note. To locate the flat 7 note, we first find the 7th note of the E Major scale (D#) and then go back a 1/2 step to the D.
So the notes of the E7 Chord are: E G# B D
Here is a key that will help you read the chart:
Chord Playing Tip: Be sure that you are pressing down on the string hard enough. You should play each string one at a time to make sure you have a nice clean sound. If any of the strings buzz or sound muted, then something is not right.
E7 Chord Video
The video below will further demonstrate how to correctly play the E7 Chord. It also demonstrates how to play some variations of this chord