1. ORIENT
The original Dead Ringer goes in either way.
On the Pro, the arrows on the sides should always point up, towards your bass strings.
2. INSERT
Slip it in sideways under your strings, just in front of your bridge.
3. TWIST
Press down gently while twisting it flat.
4. SEAT
Slide it over until it's snug against your bridge.
5. CHECK THE FIT
Strings should press firmly into the foam, not just touch it. If it feels loose, add one or more of the extra foam strips until it fits snugly.
Tip: it's better a little too tight than too loose.