Adding an Angular Component to a Pre-existing Web Application

My partner and I are working on a project that is nearly fully PHP with a SQL backend, but we've been informed that our project needs to include a Angular Component. I was looking online and most sources seem to show starting an Angular project from scratch and one page applications. We do not think that we could transfer our whole web app to Angular because of how it handles HTML versus PHP, so we were wondering if it is possible to tack on an external page, such as a very basic forum board or comment block, to our project? Could we hyperlink it from the header of our application? Do we need to create a whole separate project, app, and component for Angular incorporation, or do we need to move our PHP into an existing Angular app? Alternatively, but hopefully not, would we need to look info refactoring our whole application to meet this criteria?