Adding prebuilt and custom plugins/action hooks

Hello,

I am working on a contracted project merging an HTML/CSS intranet site with a WordPress based intranet site that was outsourced. The outsourced company only gave me access to the “themes” folder. Is there any other way through the admin portal to work with prebuilt plugins or custom plugins/action hooks? (Manager off for the weekend).

However, I’m almost sure I need access to the wp-content (whole) and wp-includes folders.

Thanks for any feedback.