I checked my site with google page speed.
It said Specify an expiration for my resources.
Can anyone tell me how to leverage browser caching for blogger?
You cannot set custom expiration for resources served by Blogger - that part is already done for you by Google servers. Having said that, if you serve content from any third party domains (which you are), then you should look into enabling compression and caching on those hosts.
Of course, sometimes this will be out of your control - ex, third party widgets which you do not control directly.