How to add custom css in Blogspot template :
1. Log in to Blogger and go to your Dashboard.
2. From the left sidebar, click on Theme.
3. On the Theme page, click the Customize button.
4.A new editor window will open. On the left side, click the Advanced dropdown.
5. Scroll down to the bottom of the options, then click Add CSS.
6. A blank box will appear where you can paste or type your CSS code.
Once you’ve added your CSS, click Apply to Blog in the top right corner to save changes.