Unless they are steam games you must reinstall them. Games make entries in the registry at install.
If they are steam games you can delete everything in the steam folder except the game folder and steam.exe then run steam.exe and steam will reinstall itself. Then launch the games from in steam and it will take care of the setup stuff without really reinstalling.
You will also need to recover your save games and move them to the appropriate folder on the SSD.
if you have space you can use steam mover to swap the current games you are playing on and off the SSD/HD to get the SSD boost for games(after they are installed)