This process works for any community whether it’s on Kbin or Lemmy, and should work in any client including Voyager. It’s the “correct” way that should work whether anyone from your instance is already subscribed:

• Get the name of the community and the name of the instance. For example, let’s say you want to subscribe to “NFL” on “kbin.social”.
• Put them together with a “!” and a @ to make an instance link like this: [email protected]
• Press search on your client and then search for that text.
• One of the options will be a link to that community (but your instance’s copy, so for me that will be https://discuss.tchncs.de/c/[email protected]). Click on it, and then click subscribe when it pops up.