Unable to find "includable id='post' var='post'" in Blog html

Problem 

Many a times widget providers ask you to put the code below.

<b:includable id='post' var='post'>

but we are not able to find <b:includable id='post' var='post'> and hence end up placing it at wrong location.


Solution
 
Step 1 - At Template -> Edit HTML 
 
Check Expand Widget Templates
 
Step 2 - Ctrl + f and find the code <b:includable id='post' var='post'>

<b:includable id='post' var='post'>