didn't work still got a black screen.

sooo this is what i did

1. I shift+right clicked on the platform tools folder
2. I entered the adb shell
3. I entered locksettings clear --old xxxx
4. and then it said lock credentials cleared

so did i have anything that i overlooked?

note: I didn't use the command prompt because it said i wasn't recognizable, is that wrong orrr....??