Here are 3 easy tips to get you started:
Wear it. The best way to break in any leather jacket is the old fashioned way – just keep on wearing it.
Roll it into a ball. Simply use your hands to tightly roll your leather jacket up into a ball. Release and repeat.
Move and flex in it. Repeat simple moves like arm circles and pushups to accelerate the “wearing” effect. (Check out this article for a few more tricks.)