I may be doing this incorrectly, or doing it correctly but with some flaw in my technique...

I have a few boards that have a slight bow in them, and I was hoping to run them through my jointer to get a straight edge. My question is, should the bow face up or down? I'm pretty much flying by the seat of my pants with this, as this is my first attempt to straighten out a board. I tried some last night, and somehow managed to get one end of the board narrower than the other end by about 3/4". Not sure how I did that....

Many THANKS for your patience and continued advice from this inexperienced, yet very enthused rookie!!

Keith