Your agent profile
Go to Settings → Branding & PDF. Under Your agent profile, enter your name, phone, company or brokerage, license number, and website, then select Save profile. These appear on the PDFs you export, on your homes' public pages, and on the transfer page your buyer opens, on every plan.
Branding (Realtor Pro)
On Realtor Pro, the same page lets you upload your Brokerage logo, add a tagline, and choose an Accent color. The preview shows how the PDF header will look; select Save branding when you're done. The company name comes from your agent profile.
Your logo, color, and tagline then appear on the property PDFs you export, your homes' public pages, and the transfer page. On Realtor Solo they don't appear, but anything you saved is kept for when you move to Pro.