Ghost supports a simple way to add code snippets, such as the Navu embed code, to your theme files without editing them. This article from Ghost explains how to accomplish this.
The snippet of code to add is shown below.
Replace the SiteCode with the specific 6 digit alphanumeric code for your site. Where to find my site code?
Alternatively, once you have signed in to the Navu application, navigate to the Domains tab. Find your site, and click on the INSTALL link. Copy the Navu embed code from there.
Once the Navu plugin has been installed, all published Guides will be visible on your site for their targeted segments, and Navu will immediately start collecting visitor data and display it in the Segments, Guides and Visitors tabs.