Level the Ramp

Once the pickup height is set, then you can attach the ramp, but first you have to adjust the angle of the ramp. The surface of the ramp should exactly match the height of the pickup and be parallel to the strings when the strings are fretted at the 24th fret.

What's a
Ramp
The ramp is intentionally manufactured to be too "shallow" so that a complete range of adjustment is available for every player. Adjust the ramp height and angle by adding layers of tape. Apply the tape in two rows, near each edge of the ramp. The way to create the correct angle (to stay parallel to the string when it's fretted at the 24th fret) is to apply gradual lengths of tape.

Attach the Ramp

Once the angle and thickness is correct, the final layer of double-sided tape can be applied.

That's all that's needed to hold it in place.

For creating the thickness and angle, any kind of regular tape will do.
For attaching the ramp, here's the double sided tape I've had the most success with:
Scotch "Poster Tape".
Half the width is plenty strong and it doesn't leave a residue.
About the Controls

Adust the Intonation