blogger(blogspot)There no predefine way to set your post as home page But You can do this by some tricking to blogger post options.Below is the simple solution is given How you can set blogger post as home page.Follow the given steps to set your post as home page.
Please Follow Steps in given video Or Follow steps in given image steps
Go to Edit Post And Select the post to which you want to set as home page
Now your post is load with editor.Go to end of your editor where there is link for POST Option.
After clicking on post option you can see all post related options
Now set the post date and time as feature date time and your post becomes the home page of your blog.You can change any post to feature date.