Ability to add custom CSS code snippet interactively is another nice feature of Blogger's new Template Designer (BTD) I want to address here (to which I might later refer).
|Log in to your Blogger-In-Draft dashboard at draft.blogger.com and enter the Template designer (as previously explained)|
|On the BTD page, click Advanced, then Add CSS tab (see picture above)|
|Add your CSS codes on the opened Add CSS window. Changes you make will reflect instantly in a live preview beneath the editor.|
|If everything goes o.k., click "APPLY TO BLOG". Done!|
You might want to read the Blogger's official page about this issue.