Back in those days, you cannot edit or change its URL once you have published Blogger blog post. You can only edit the name of the blog post.
Now you can do that with Blogger published posts.
There are two (2) main steps which you need to do.
*Note: Before changing the permalink of your published Blogger blog post, you must save a copy of your old URL in the Notepad which we need to use it in STEP TWO.
Here is a quick guide on how to change published Blogger URL.
STEP ONE: Change URL
1. Go the particular blog post which you like to edit its URL.
2. Click the word "Edit" below the post name.
3. Your written blog post will appear.
4. First change the blog post title as you wanted above the page.
5. Next, click on "Revert to draft" button which is located on the top right hand side of the page. (Above the words "Post settings")
6. Now click on the word "Links". It is located below where you have just clicked "Revert to draft".
7. It will drop down a menu as shown below.
9. Now edit the blog post title as you wanted.
10. Then click the "Done" button just below it.
11. Finally click the "Publish" button above.
Now this particular blog post has a new URL as you wanted. So the old URL is now broken.
If you click on its old URL, you will get this remark: "Sorry, the page you were looking for in this blog does not exist."
Now you need to do a redirect for this broken link.
STEP TWO: Redirect Old URL To New URL
Here is how to redirect your old URL to new URL using Blogger custom redirects.
1. Log in to you Blogger account.
2. Click on "Settings". Then click on "Search preferences".
3. It will open a new page. Under "Errors and redirections", click on the word "Edit" next to "Custom Redirects", as shown below:
4. Paste the old URL into the first box next to From: http://.
5. Paste the new URL in the space next to To:
*Note: Do Not enter the full URL. Omit the Blogspot domain name for both entries. It should start with a slash followed by year-month, slash then the blog post name.
See the example below:
7. Click "Save" and you can see the word "Yes" next to "Permanent:"
8. Finally click the orange color "Save changes".
9. That's all.
If you have done it correctly, now if you click on the old URL, it will automatically redirect to its new URL.
*Besides having a broken link, your old URL will have some ranking in search engines as well as it will have some backlinks. In order to its maintain ranking and backlinks, you must redirect old URL to new one.