Okay, in the little space between the box you write in and the box you read?
There's a button. It likely says "local" on it. But it may say general, local, whisper, group, or party.
Click it. Select "group" for your words to be the bright green.
General talks to everyone in the map. Select general, and type.
Local is white, and it talks to the characters around you in the map.
Party is orange, and it talks to people you have added to your party.
Group is bright green. You want this one for now.
Whisper is aqua blue, and it needs someone specified in the box to talk to. It only goes to that one person alone.
If you uncheck any boxes, that means that you CANNOT see those categories in your box. Check them if you want to see them. (("Action" is where you can turn off people buttswinging and roaring and such))