There are two ways:

  1. Automatic: in UTM Integrations, open your project and click Include UTMs in campaigns. The project's UTM pattern is applied to the ads in the account.
  2. Manual: in Meta Ads, click Bulk edits, select the ads and use the URL Parameters (UTM) edit to fill in whichever parameters you want.

The UTM Integrations page is where your projects and the sales webhook live: it compares the purchases reported by Meta with the real sales tracked by UTM. Connecting an ad account doesn't happen there: use Connect Meta and Connect Google.