Sajari is currently a "custom HTML tag", you can select this when adding a new tag as per below:
Sajari is typically a global install, so you can activate across your entire site as per below. Don't worry about hiding various pages from your site search, you can easily omit them later using "crawling rules".
You can access your install code from within the app itself (if logged in). You will also be emailed a link which you can provide to your developers. Paste the code as per below:
Once you've completed the above steps, your content will begin to index and build statistics around popularity, recency, etc to optimize your search and recommendations. You can then add simple site search plugins and/or recommendations easily by following instructions here. Alternatively you can build advanced interfaces using our ReactJS SDK, which offers much greater functionality including facets, autocomplete and more.