(New to) Moving blog site over to new site to create multisite setup

I have a new WP site install on a new host with a bunch of custom post types and taxonomies. This was a slight redesign and site move from another host/platform over to WP. Everything is good so far. The only plugin I’m using is the Yoast SEO plugin.

We’re not using this new site as the ‘blog’. There’s already another WP site with a different design that is the blog. What I need to do now is move over the existing blog site over to the new host and have it in a subdirectory.

I started reading about the multisite setup and I think a requirement for an existing install is a subdirectory, which is preferred. Not knowing that much about the multisite setup, is that something that I should be able to do. Have an existing site, then a blog or another site within a subdirectory on the same host? Will I or can I have a separate WP Admin for the other (blog) site in my multisite setup?

Thanks!

here’s the new site: https://kerrygoldusa.com/ and the blog I want to move is current just linking over to it from the new site.