Do you want to add tags to your bloggers post?

just add

<b:if cond='data:blog.url == &quot;http://URL Post&quot;'>
<meta content='Description of your post &quot; /&gt;' name='description'/>
<meta content='Tags of your post' name='keywords'/>
</b:if>


to add those codes to blogger login to your blogger choose layout>>>Edit Html.
then add those codes after : <b:include data='blog' name='all-head-content'/>

And click save