Hi,thanks for posting the question to H.C.M. Forum.
Lean & thin a type of personal body appearance.
So for this you have to do few step but with complete dedication as,
High protein diet but push and up exercises regularly for at least 8-9 hours at peak level.
Begin with 1 hour daily and gradually increase the time.
As push and up will increase the size of
Biceps, Triceps,Deltoid muscles including muscles of back.
2 ND Step is up & down and increase the speed as gradually up to 100 in a single step.
Beside protein diet you have to use fatty diet which will increase in fat of your body.
Please note down that you require 2000 -4000 calories per day according to nature of work.
If you will take more calories and regular exercises than girth of muscles and body will take size and good look.
DEDICATION is the thing which you require.
Dr. HET