Okay. That's easy:
to get everyone's attention you can shout - click on where it says Talk: in the toolbar bottom left and it will give you various options e.g Talk (to those nearby), Shout (to everyone, no matter where), Party (to those in your party, once you have joined one), Whisper, only to those very close etc.
Also to start a conversation to a specific player you can bring up the players tab, highlight the one you want and select "Tell player" from the list in that box. If they have already instigated it you can simply click on their icon in the conversation bar and that will bring up their name for you to talk directly or, to show off, you can type e.g. /t "Hogan the bow Sharp" and then whatever you want to say to that player (except if it is me because nobody has the characters on their keyboard to talk to me like that
)
Hopefully that will get you started.
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