There are 3 ways:
1. You have to create a picture containing the text (called HUD) for every message you want to appear and make them display via scripts for objects or zones
2. You use FPCRAWTEXT which was inluded beginning with FPSC 1.16 to display typed text messages (a SINGLE line only at a time, in addition icons or graphics cannot be displayed with this method) via scripts as above.
This thread gives you an idea: http://forum.thegamecreators.com/?m=forum_view&t=171157&b=23
3. You use RPG mod. It's not that easy to understand but very rewarding. RPG mod allows you to maintain a standard that comes close to pro games (conversations, multiple choice, free text entering)
In case you find my grammar and spelling weird ---> native German speaker ^^
