Here is how to add meta tags to your blogger(blogspot)

1.Sign in to your blogger dashboard>click the 'layout' button[see the screenshot below]

2.Click on the 'Edit html' tab

Here is the code you have to add
<meta content='DESCRIPTION HERE' name='description'/>
<meta content='KEYWORDS HERE' name='keywords'/>
<meta content='AUTHOR NAME HERE' name='author'/>
DESCRIPTION HERE:Write your blog description
KEYWORDS:Write the keywords of your blog
AUTHOR NAME:Write the author's name(Your name)

3.Add the above code just after this
<b:include data='blog' name='all-head-content'/>

Don't forget to add description and keywords.
and save the changes.