Talk to an NPC, simple be in the same square/room as them, click the scanner and click the talk button that appears.
As for the merchants, you heard wrong, or the other person was wrong. The Merchant NPC does nothing. There is a Shop Keeper NPC that is admin owned only and are only in the NPC only facility, Shops. These allow you to buy some of the small items (knives, staffs, workers coverall etc) for an insignificant amount.
Its weird as this is the description next to the merchant NPC when you go to the NPCs category under general.
"One of the galaxy's many traders, offering a small selection of items to the player for a price. Why not? After all, he has a wife and kids to feed, right?"
How do you explain that?
A lot of the rules have descriptions that were put in before it was actually implemented. This means that every so often there will be some rule that slipped through that doesn't match up with what it actually does now. This is one of the reasons there is a Rules Update forum, so when these issues arrise, a more accurate description can be supplied.