This is going to be short, I am not going to keep beating around the bush.

Here are the steps to update your existing Blogger theme to include Micro data in it.

Step 1:

Login to Blogger

Step 2:

Select Theme from the left menu

Step 3:

Select Edit HTML option under the theme preview

Step 4:

Click inside the box with the HTML code and press "Ctrl" + F (For PC) or "Command" + F (For Mac)

Step 5:

Search for

<b:widget id='Blog1'

Step 6: Replace it with

<b:widget id='Blog1' itemscope='' itemtype='http://schema.org/BlogPosting'

After replacing, it should look look like this

Step 7:

Search for

'post-title entry-title'

Step 8:

You will see a code similar to this

<h3 class='post-title entry-title'>

Depending on your template you will see the same with h1 or h2 or h3, this should not be a problem.

Add

itemprop='name'

next to

class='post-title entry-title'

and it should look like this

 <h3 class='post-title entry-title' itemprop='name'>

Step 9:

Search for the code

<b:if cond='data:post.dateHeader'>

Step 10:

You will see a similar code along with it.

 <b:if cond='data:post.dateHeader'>
          <h2 class='date-header'><span><data:post.dateHeader/></span></h2>
        </b:if>

Now you need to replace the <span> shown in red with the following code

<span itemprop="startDate">

It will look like this after the update

 You are done.

With these quick edits you will be able to have search engines capture the Micro Data from your Blogger site, yield a better user experience and search results.