For adding a meta description first we should go to blogger dashboard and then settings > Search preferences > meta tags > description and after this click on this option for edit purpose.
Select "yes" for enable search description and post your blog description in the box and then click to save changes.
How to add meta description in individual posts:
Go to your post and edit the page and then look search description in the post settings.
Click search description option and enter your post description and then click to done button. Now you successfully save your post meta description.
You can also add meta description manually in the blogger template, for this purpose go to template and click to edit HTML and than post the following code before <b:skin><!
<b:if cond='data:blog.metaDescription != ""'>
<meta expr:content='data:blog.metaDescription' name='description'/>
</b:if>