How do you set flashpoint difficulty?.. also is there really no search function on these forums or am i blind?

At level 50, when you talk to the npc outside of the flashpoint, they will allow you to select normal or hard mode. Only level 50s can do hardmode. Also, not all of the flashpoints have a hard mode. Esseles, ilum, false emperor, taral v, maelstrom all have hard modes (i might be missing 1).

 

I've only done esselles, false emperor and taral v on hard mode. Esseles and false emperor are fairly easy once you learn the tactics. Taral V isn't much harder, bulwark is hard enough, but once you know the tactics he's just a dps race tbh.