We are talking about chord construction in this lesson if you don't understand any of this see my lesson Universal key.
A major chord consists the 1,3,5 notes. We will be using the E chord to look at.
The first note is E this is the root or where the chord gets its name. What is the third of E, that would be G# (you would count three whole steps from E to find this E,F#,G#). Now what is the fifth note, B (E,F#,G#,A first Tetra chord and B,C#,D#,E second tetra remember the second tetra chord begins with the perfect fifth).
Notice if you read from the sixth string to the first holding this chord you would only find these notes. This is how it would read 6-E,5-B,4-E,3-G#,2-B,1-e.
Now that you have the idea I will just list some other formulas