To get Major 7th or M7 Chord, move the Middle Finger down 1-step.
Let's dive in quickly. Deriving AM7 from A:
Final AM7 :
Take a look at he A-chord again...
AM7 looks like this (note: the fingers are rearranged like in Am) :
Deriving EM7 from E...
EM7 is:
AM7 looks like this (note: the fingers are rearranged like in Am) :
Deriving EM7 from E...
EM7 is:
In actual: E-chord (you should know it now!) and EM7 are: