The Scanner is located at the center bottom on your main screen.
You can use your Ship Scanner to discover usable salvage in the system you're in. The result varys, depending on if the system you're scanning in is occupied by one of the factions, i.E.: It's more likely that you recieve an Bajoran transmission when you scan in a system occupied by them, rather then in Dominion Space. You also can find items, tied to the owner of the system.
Once you used your Ship Scanner, it gets a cooldown of 3 hours. If you are at least at VIP Level 2, you can speed up the timer by spending Dilithium. The amount depends on the time left.
When scanning, you can find various amounts of the following: Credits, Components (any rarity), Equipment (any rarity), Ship Schematics (1 to 10), Transmissions (usually one).
You can't acquire Crew member, Merits or Dilithium when scanning.