1. Shut off the water.
2. Remove Plastic rough-in spacer. It's black and it's only there for roughing in, and so the tilers don't come too close.
3. Unscrew silver retaining nut - should only be hand tight. Remove and discard grey cap that was being held is place by nut. Remove and discard plastic stopper inside faucet.
4. Take grey plastic disk off of cartridge and DO NOT THROW AWAY. Adjust gearing/splines to hottest temp by rotating plastic insert. Reinstall plastic disk.
5. Install cartridge with HOT lettering to LEFT. Secure with Silver Nut.
6. Slide large O-Ring over silver nut.
7. Install trim plate using long phillips(star) screws provided (2)
8. Slide Plastic spacer (looks like a snowflake) into chrome trim (cylinder) and slide cylinder over Silver Nut.
9. Install handle by tightening allen screw until it engages firmly with cartridge.
Changing Existing Trim:
As Above Except Old Trim Must Be Removed First. Cartridges Are Specific To Certain Trims. Even More So If Installation Is Over 3 Years Old. 3 Years Ago, Delta Went To The "Universal Rough-In" Which Made Things A Little Easier Because The Appropriate Cartidge Now Comes With The Appropriate Trim.