chasmcg...I know I place my mouse over the midi note and pull down in some manner but for some reason it's not working...
You've already gotten expert replies from Scott and g_randybrown - I just wanted to add that the technique of finding the sweet spot as you hover over a note, until you see the velocity lines, and then dragging up or down, is a bit of a tricky maneuver that takes practice. I still find it a bit slow-going, so don't use that method very often.
An alternate method, and what I find to be the quicker way to edit velocity values is to simply get my cursor over a note's displayed velocity in the velocity pane, and edit it directly. For me, that's faster and more reliable than the hovering to find the sweet spot.
Do take note that there are methods of changing the relative value of all the notes in a clip or track, as randybrown pointed out, another method being to use the velocity MFX, or the simple Velocity menu item that can change a range of notes by percentage.
Randy