Ah right, I apologize. I must have written that in a hurry or something.
First time:
Download
TREExplorer and save it somewhere
Open it up and go to file->settings->Associations: Make sure IFF is checked.
Press "Ok"
File->Open->Tre/Toc and navigate to your SWG directory, and select sku0_client.toc. This is a Table Of Contents file, that is also loaded by SWG. This picks the latest version of everything from the TRE files.
After it finishes reading it you will see a folder tree on the left side, navigate to datatables, then clientpoi. Right click clientpoi.iff and choose Export. Navigate to your SWG directory, and create the folder datatables/clientpoi and save clientpoi.iff in there.
Thus making it look: SWGDir/datatables/clientpoi/clientpoi.iff
Now for whenever adding POIs
Go to your SWG dir, datatables, clientpoi and double click clientpoi.iff
Then just scroll to the bottom and add a new one, dont bother with the @StringTable:KeyName format as name/description as that tells the game to point it to the stringtables, can just put the name/description in there and it'll display as []:Name, with Name being the name you put in. This has the added benefit of your custom POI's showing up at the bottom of the list.
Then put in the X Y Z coordinates (Y is Z and Z is Y in that list! So usually you'll want Y to be 0).
Save the file. Restart your game, and you're done!