Pretty much the same as masonc said, it’s only your 2nd attempt, you have to give it some time to see if it works.
Remember to keep trying, even if you don’t get Lucid Dreams (i had a decent ammount of them some month ago, and it still took me a month to get one again, so DON’T GIVE UP! you WILL get them if you keep trying, and if it really doesn’t work then just change technique 
)
little sidenote: Try waking yourself up saying the mantra “I’m goingto wake up in 4 hours (or next time i’ll dream/etc.)” It’s less “traumatic” than an alarm, and it never let me down, not even once (but i fall asleep quite often without even saying it 
)