The IKEA directions for the table legs installation, while not very helpful, are completely hilarious.
I used a 1/8" drill bit for the screws that came with leg bracket, and pre-drilled all the holes necessary. BE VERY CAREFUL NOT TO SINK THE DRILL BIT TOO DEEP! Otherwise you have holes in your table top.
While pre-drilling I used a clamp to hold the bracket in place, then drilled the screws in.