You need two identifiers to unlock the pipeline:
1. Google Ads Customer ID
Open Google Ads. Top-right corner, next to your email — you'll see a 10-digit number formatted like 123-456-7890. That's your Customer ID.
2. GA4 Property ID
In Google Analytics, navigate to Admin → Property Settings → Property Details. Look for the numerical Property ID (e.g., 32455612). This is *not* the "G-" measurement ID used for tag installation.
Why both?
Google Ads tells the engine what you spent. GA4 tells it what happened after the click — conversions, bounces, revenue. Without both, the engine is flying blind and can't calculate true Return on Ad Spend.