Kendall measures your ad performance by combining two things: the spend it pulls from each ad platform, and the clicks and orders it records from the pixel on your store. Connecting an ad account is what brings in spend, ROAS, and cost per acquisition across your reports. You do it once per platform.
Kendall only ever requests read-only access. It can't change your ads, budgets, or creatives.
From the Account Setup page you'll see a card for each platform:
You can track several ad accounts on one platform as long as they're under the same login. To add a second Meta account: