This is what you do:
1. Log in to your Blogger account.
2. At the Dashboard, pull down the slider and click on "Template".
3. Then click on the "Customize" button.
4. Next click on "Advanced".
5. Pull down the slider and click on "Add CSS". A box will appear next to it.
6. Now paste the code below in the empty box provided.
.post-title {text-align:center;}
7. Finally click on "Apply to Blog" button.That's all you need to do.
REMINDER: Copy the code carefully. There is a dot in front of the code.