"How to change realmlist? What would I even need that information for?"
Changing realmlis(.wtf) is crucial for anyone who wants to play WoW (World of Warcraft) on a private server, or change back the realmlist to the original one (after playing on private server)
1. First of... You have to get a new realmlist from somewhere ( the new private server where you are going to play), for example this one set realmlist logon.molten-wow.com It is taken from the leading and best private server called Molten-WoW. It is in my opinion the BEST private server around. Check it out here.
2. Second comes the often most difficult phase; finding the realmlist.wtf (works for both Mac and PC): a)
Mac: Just type realmlist.wtf in Finder or Spotlight and you will find it.
PC: Search the realmlist.wtf from the search bar (I'm sorry that I can't give you more detailed information because I don't have a Windows PC :s).
b) You can also go to: World of Warcraft (folder)>Data>enUS (or enGB + others)>realmlist.wtf.
3. Open it (with TextEdit or ANY other text editing software: Word, Pages etc...)
4. Copy-paste/write the realmlist in it:
5. Now save it. What you might want to do is delete your cache folder from the World of Warcraft folder because it might slow you down (don't worry, when you launch World of Warcraft (.app/.exe) it will "re-create" the Cache folder automatically).
Now you are ready to go; just open WoW (with worldofwarcraft.exe/worldofwarcraft(.app)/World of Warcraft (application)), login, choose a realm, and start playing!!!