I tear off a piece about the size of a fingernail, and hold the torn edge about 1-2mm from the edge of the flint shard (on top of the flint) and then strike the flint with the steel. I've only tried about half a dozen times, but got an ember within a few strikes every time.
I use the flint shard and striker that came in the tinderbox. All I can say is keep trying, as getting a good spark is a matter of trial and error. Altering the angle of strike or making sure you've got a good sharp edge on the flint can make a significant difference.
No man knows true happiness until he's married......but then it's too late!
Proud member of the Greater Manchester Bushcraft Group