Right now, there is no import/export. It’s a known useful feature, but the devs have no time to work on it (I’ve been following all the optimization work they’ve been doing on github, I don’t know if they sleep). You’ll have to start over atm, sorry.
Go to Communities at the top, change the filter from “Local” to “All” and search for “Gaming”.
If you’re the first one who wants to register to a community from this server (not the case here) it’s slightly more complex.
Nope. You can subscribe/post/comment on any community on any instance. There is one small seam though: if you’re the first person to subscribe from your instance, you need to put in the full URL of the community (https://lemmy.ml/c/gaming, for example) to pull it into your instance.
After that, everybody on the same instance as you will see it when searching for communities just like it was local.
EDIT: Oh, forgot to mention: make sure the search is set to “All”, not “Communities” when you do this.
Having understood the fediverse on a theoretical level but not ever actually stepping into it, it’s really amazing to see the interconnectedness of it in real time :)
That’s actually not how it works. Images are hosted by the instance the community is on. Other instances embed those images as links in the page. The image is downloaded from the original instance by the browser.