Search this code or similar <div class='post-body entry-content>,
Then paste this code under it
<b:if cond='data:blog.pageType == "item"'>
<style>.fullpost{display:inline;}</style>
<p><data:post.body/></p>
<b:else/>
<style>.fullpost{display:none;}</style>
Then, find <data:post.body/>
Paste this code after <data:post.body/>
<a expr:href='data:post.url'>Read More...</a>
</b:if>
Then Save!
Go to Setting=>Formatting=>Post Template
Fill the form with this code:
<div class="fullpost">
</div>
Then Save!
Notes:
There a default text on your New Post like this:
<div class="fullpost">
</div>
You can make Summary text using "Read More" like this:
TEXT TO SHOW
<div class="fullpost">
TEXT HIDDEN
</div>
Source: tutorial-website.blogspot.com
