Can I Install Indigo theme on WordPress Sub-Directory?

I’m running a coupon sharing site and it has a Blog & Articles section. However, in the Blog section, I’ve already installed another WordPress installation and I have already used a different theme on the Blog section there. But I want to use a different theme (Indigo theme) on the Article section as well here but it’s the same WordPress installation so on the article section, can I use this or a different theme than the main WordPress theme?

Help in this regard would highly be appreciated.