How can i make edit post

First you log in or sign in your domain (your website URL)
Example: http://part-timedataentryjobs.blogspot.com
see your website upper right corner sign in option.Now you click sign in option and log in here.
    you will see New Post button and see right side Edit Post option. Now you click here and edit you old post.
Example Image

Click Edit.you have to choose your post and edit something and then published post button.