chore: improve enrollment documentation

apps/docs/content/docs/organization.mdx

@@ -1,12 +1,42 @@
 ---
 title: Organization
-description: Learn about organizations in ClassroomIO.
+description: Overview of organizations in ClassroomIO — settings, branding, domains, roles, and related guides.
 ---
 
 import { Callout } from 'fumadocs-ui/components/callout';
 
-<Callout type="warn" title="Work in Progress">
-  This page is a work in progress. Help us expand it by contributing!
+An **organization** in ClassroomIO holds courses, people, branding, and your academy. Every admin and student belongs to an organization. This page points you to the right guides for setup and day-to-day management.
+
+## What you configure at org level
+
+| Area | Where | Guide |
+| --- | --- | --- |
+| Name, logo, brand color | **Settings → Organization** | [Customize Your Organization](/docs/how-to-guides/customize-organization) |
+| Public homepage | **Settings → Landing Page** | [Customize Your Academy Landing Page](/docs/how-to-guides/org-landing-page) |
+| Custom domain | **Settings → Organization** | [Set Up a Custom Domain](/docs/how-to-guides/custom-domain) |
+| Team roles | **Settings → Organization** | [Roles and Permissions](/docs/how-to-guides/roles-and-permissions), [Inviting a Team Member](/docs/how-to-guides/invite-team-member) |
+| Signup rules, Internal Enrollment Only | **Settings → Authentication → General** | [How Course Enrollment Works](/docs/how-to-guides/course-enrollment) (org access section) |
+
+## Default URL
+
+On creation, each org gets `https://<siteName>.myclassroomio.com` as its academy URL. You can connect a [custom domain](/docs/how-to-guides/custom-domain) so students use your own hostname.
+
+<Callout type="info" title="Academy vs admin app">
+  Share your academy URL with students. The generic `app.classroomio.com` host is for platform access when no org subdomain applies. Course and enroll links should use your academy when possible.
 </Callout>
 
-We will write about organizations here.
+## Courses and programs inside an org
+
+- **Courses** are individual learning containers. See [Course](/docs/course).
+- **Programs** group courses with shared goals. See [Programs](/docs/programs).
+- **Students** use the [Student Dashboard](/docs/student-dashboard) after they sign in.
+
+## Related guides
+
+- [Customize Your Organization](/docs/how-to-guides/customize-organization)
+- [Customize Your Academy Landing Page](/docs/how-to-guides/org-landing-page)
+- [Set Up a Custom Domain](/docs/how-to-guides/custom-domain)
+- [Roles and Permissions](/docs/how-to-guides/roles-and-permissions)
+- [How Course Enrollment Works](/docs/how-to-guides/course-enrollment)
+- [Course](/docs/course)
+- [Programs](/docs/programs)