docs: skeleton and links

website/docs/topics/joining-an-existing-instance.mdx

@@ -0,0 +1,21 @@
+---
+title: Joining an existing Unleash instance
+---
+
+Welcome as a new user in an Unleash system!
+
+(See [this slide](https://docs.google.com/presentation/d/1oc7o-1vylGVsm7az0BqJw1LXjuf4NYtw6jS15iNXL-0/edit#slide=id.g1450e3dffa3_0_0))
+
+## Conceptual overview
+
+### Features, strategies, and other important parts
+
+## Logging in
+
+## Admin UI overview
+
+## Because it's an existing instance, what is already set up
+
+## "Why can't I see X"
+
+## Project roles

website/sidebars.js

@@ -299,7 +299,11 @@ module.exports = {
                     'Discussions, explanations, and explorations regarding topics related to Unleash.',
                 slug: '/topics',
             },
-            items: ['topics/a-b-testing', 'topics/proxy-hosting'],
+            items: [
+                'topics/a-b-testing',
+                'topics/proxy-hosting',
+                'topics/joining-an-existing-instance',
+            ],
         },
     ],
 };