where do I do stuff between Network & Admin

Alright, I am going to ask enough stupid questions until I get this figured out to the point I can explain it to others. TheTropics.com (not really) is set up with MU with subdomains. I uploaded DailyTheme to content>themes. Activated it in Network, then Activated in Admin. I hope that is correct. I could not find it in Admin until I activated in Network.

In Admin, I added some Post Categories and some Hello World! posts to fill in the theme. This is where I get confused. I want the site to make sense to an old-school newspaper editor. So TheTropics.com is going to have local editions. Now that I know it is possible, how do I add set by step coconutisland.thetropics.com? Or should I be looking for support doc for that? I just want to teleport you to my office every other day lol.