Unlike wordpress blogger, blogspot don’t have direct method (I said direct not ‘NO’!) to add categories to your posts.
Just adding ‘Labels’ while you post your posts won’t work always.
But it’s simple to categorize posts in your blogspot.
Follow the simple steps below. (Google is always simple & will be!)
1. From your ‘Dashboard’ , Go to ‘Design’
2. Click ‘Add a Gadget’
3. Add ‘Labels’ from ‘Basics’ gadgets by clicking ‘+’ sign.
(Just scroll down to 17th or 18th item, you won’t find it by search sometime!)
4. Now you can add any number of Labels with commas while you post in Label Box
5. Done! Now Labels or Categories of your posts will be in your blog.
Very simple, right?