Where the CHARACTERGUID is the NPC who is going to move and talk and "sallyDialog" is a dialog file you created in the dialog editor.
In KB put for example
Code
IF
(whatever condition)
THEN
CharacterMoveToAndTalk(CHARACTERGUID_sally1_42888c50-7b31-41a5-8703-05672163b2e5,_Player,"sallyDialog",0,"sallyDialog_Ended",1,5.0);