chore: Prepare for publishing the extension

README.md

@@ -1,3 +1,18 @@
 # Universal Inbox
 
-Manage Universal Inbox notifications from Raycast
+Manage your notifications in a single [Universal Inbox](https://www.universal-inbox.com)
+
+## Setup
+
+To use the Universal Inbox extension for Raycast, you will need to configure an instance URL and an API key.
+
+### Instance URL
+
+The default instance URL is: https://app.universal-inbox.com
+Get the URL from the Universal Inbox instance you are usually connecting to.
+
+### API Key
+
+You can get an API Key from your Universal Inbox user profile page:
+
+![user profile page](media/ui-user-profile-page.png)