For adding some search description for search engine for Google just take the following steps.
Go to Settings and then select Search Preferences and click Edit.
In "Description" Text filed Select Yes and then , write in your Description of Post and click Save changes.

Descriptions must be related with your post and describe the whole contents of your post in few line. For example "Creating a new post in Blogger.com.
Enabling this feature will display a “Search Description” option in the Post Settings panel.
This allow you to enter a search description for your individual posts.
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