Upload the companies in your book so Discover and agents only find people who work there.
Open Settings → Prospecting Accounts → "Manage my accounts" (or /my-accounts).
Upload a CSV of company domains (one per row) and click "Upload accounts".
Or click "Paste" and drop in a list of domains.
Paste domains one per line, then save.
Filter the list, or "Remove all" to clear it.
Admins choose the mode under Org settings → "Account scoping": Open, or Named accounts so each rep stays inside their list.