So first off, I am unaware of a kbin-specific magazine browser across all instances, so you will likely need to visit each kbin instance at https://fedidb.org/software/kbin to see what magazines they have you might be interested in. For comparison, Lemmy has https://browse.feddit.de/ if anyone reading this needs that.
Once you have the names of the magazines you would like to subscribe to, the easiest way I found was to just open a text file and create a bunch of lines with the following syntax:
https://[your instance]/c/[kbin magazine name]@[kbin instance]
So since you're on lemmy.world, say you wanted to subscribe to gaming on kbin.social and firefox on fedia.io. You would sign into lemmy.world, paste in the following URLs, and click subscribe:
https://lemmy.world/c/[email protected]
https://lemmy.world/c/[email protected]
Do note that if you are the first person on your instance to try this, the URL will fail, and you will have to try again a bit later once your instance has had some time to make a copy of the magazine. Also, if you see a "Pending Subscription" message, in my experience, that does not resolve itself, and you will just need to try again a bit later and it will go through instantly.
If you are on a larger lemmy instance where someone has already done this legwork, odds are you can just search for them in the community browser on your particular instance. Using lemmy.world again, that would be https://lemmy.world/communities, where you can search for "gaming" and [email protected] is currently the eight result. If you search "firefox" it's the third result.