How do you customize your secondary blog on tumblrs new layout?

Tumblr has recently changed its layout and I want to customize my second blog but I can't find the settings or customizing button anywhere for me to change its theme. Help please.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).