Yes, radicale works great, but the UI is pretty spartan. It will manage the data, but requires a client to make edits or view the content.

First, you will have to export any existing calendar and contacts as files. It depends on what you're currently using. Contacts should probably be a vcf file, and a calendar should probably be an ics.

Next, use the ↑ button in radicale, select the exported files, and it will create a new "collection" as shown in your post. You can also create a new empty collection to use as you wish. Radicale will not merge files, but you can use a client to do that once you have created the collection in radicale.

You will have to find a client that will sync. On Android, DAVx5 will integrate it into the system so basically any client can access it. Certain Android apps may connect directly, but it's pretty hit or miss. On desktop, I use Thunderbird which works very well, but there are other options. You will use the blacked-out URL in your post to add the contacts and calendar. Check the individual app documentation or make another post if you want help.

Oh, and the last thing... Of course the client will have to be on the same network. If you want to access it remotely, you will want to set up something like wireguard (I use Tailscale, which is dead simple).