Two settings tabs look related and are easy to mix up:
Correct creative direction in Brand Guidelines. Do not expect to edit Training Data.

The sticky header shows the brand name, website, Extract from website, and Save Guidelines.
Use this when you first set up the brand, or after the website changes.

What extraction actually fills today:
It does not currently write Voice & tone, layout, or CTA guidance — even though the confirmation mentions some of those. Review those sections yourself.
The form does not always live-refresh when processing finishes. Reload Brand Guidelines if sections still look empty after a few minutes.
Work top to bottom. Missing colors, fonts, logos, and assets show a Not set badge.
Add colors with a hex value, name, Usage Rule, and a role: Primary, Secondary, Accent, Background, Text, CTA, or Other.
Upload PNG, JPG, SVG, WEBP, or AVIF. Set a name, variant (Primary, Secondary, Icon, Wordmark, Monochrome), and a usage rule.
Add a Google Font or a Custom Font (TTF, OTF, WOFF, or WOFF2, up to 10 MB). Set family, usage (Heading, Body, Accent, CTA), weight, style, and a rule. Expand typography rules for heading/body style, minimum size, text-to-image ratio, line height, and letter spacing.
Upload product and lifestyle images, textures, patterns, backgrounds, overlays, watermarks, or style references. These tell generators what the brand looks like. They are not a replacement for the brand Media Library, which stores production files you reuse across jobs.
Set logo placement, CTA placement, safe-zone margin, and extra layout rules.
Expand Advanced guidance for:

Empty copy: No scraped data found yet for this website. Run Extract from website from Brand Guidelines, and confirm the website on General is reachable.
Some teams see Knowledge in the brand sidebar. Managers can add a PDF (up to 50 MB) or a website. Those sources become suggestions for colors, typography, and tone of voice. Nothing is applied until you Accept a suggestion, which writes that field into Brand Guidelines.
If you do not see Knowledge, ignore this section — Brand Guidelines is the source of truth.