help: Add switching-between-organizations.

This is in response to a support ticket where the user had a closed left
sidebar, had added an organization, and then couldn't figure out how to
switch organizations. They had googled and found "The desktop app makes it
easy to switch between different organizations" in our help docs, which was
not sufficiently helpful.

templates/zerver/help/include/sidebar_index.md

@@ -16,6 +16,7 @@
 * [Change your language](/help/change-your-language)
 * [Use 24-hour time](/help/change-the-time-format)
 * [Joining an organization](/help/join-a-zulip-organization)
+* [Switching between organizations](/help/switching-between-organizations)
 * [Logging in](/help/logging-in)
 * [Logging out](/help/logging-out)
 * [Keyboard shortcuts](/help/keyboard-shortcuts)

templates/zerver/help/join-a-zulip-organization.md

@@ -47,7 +47,7 @@ link via another method.
 
 * If you are joining multiple Zulip organizations, we recommend
   using the [Zulip Desktop app](../apps). The desktop app makes it easy to
-  switch between different organizations.
+  [switch between different organizations](/help/switching-between-organizations).
 
 * If your company uses single sign-on (SSO) authentication for Zulip,
   these instructions may not apply. Try going to your company's Zulip URL

templates/zerver/help/logging-in.md

@@ -7,13 +7,50 @@ Organization administrators can
 [add other authentication methods](configure-authentication-methods),
 including SSO or LDAP integration, or disable any of the methods above.
 
-To log in, go to your organization's Zulip URL and follow the on-screen instructions.
+You can log in with any method allowed by your organization, regardless of
+how you signed up. E.g. if you originally signed up using your Google
+account, you can later log in using GitHub, as long as your Google account
+and GitHub account use the same email address.
 
-!!! tip ""
-    You can log in with any method, regardless of how you signed up. E.g. if
-    you originally signed up using your Google account, you can later log in
-    using GitHub, as long as your Google account and GitHub account use the
-    same email address.
+
+### Log in to a Zulip organization for the first time
+
+{start_tabs}
+
+{tab|desktop}
+
+1. Open the **left sidebar** (`Ctrl+Shift+s` or `Cmd+Shift+s`).
+
+1. Set your [proxy settings](/help/connect-through-a-proxy) or add a
+   [custom certificate](/help/custom-certificates) if needed (rare).
+
+1. Click the **plus** (+) icon.
+
+1. Enter your Zulip URL, and click **Connect**.
+
+1. Follow the on-screen instructions.
+
+{tab|mobile}
+
+1. From the home screen, tap your **profile picture** in the lower right.
+
+1. Tap **Switch account**.
+
+1. Tap **Add new account**.
+
+1. Enter your Zulip URL, and tap **Enter**.
+
+1. Follow the on-screen instructions.
+
+{tab|web}
+
+1. Go to your organization's **Zulip URL**.
+
+1. Follow the on-screen instructions.
+
+{end_tabs}
+
+For subsequent logins, see [switching between organizations](/help/switching-between-organizations).
 
 ## Troubleshooting
 

templates/zerver/help/switching-between-organizations.md

@@ -0,0 +1,32 @@
+# Switching between organizations
+
+This article assumes you've [logged in](/help/logging-in) to each organization at least once.
+
+{start_tabs}
+
+{tab|desktop}
+
+1. Open the **left sidebar** (`Ctrl+Shift+s` or `Cmd+Shift+s`).
+
+1. Click on your organization's profile picture.
+
+!!! warn ""
+    You can ask your organization administrator to
+    [set an organization profile picture](/help/create-your-organization-profile)
+    if they haven't already.
+
+{tab|mobile}
+
+1. From the home screen, tap your **profile picture** in the lower right.
+
+1. Tap **Switch account**.
+
+1. Tap on the desired Zulip organization.
+
+{tab|web}
+
+You can log in to multiple Zulip organizations by opening multiple tabs, and
+logging into one Zulip organization in each tab. To switch Zulip organizations,
+just switch tabs.
+
+{end_tabs}

zerver/lib/bugdown/tabbed_sections.py

@@ -48,6 +48,10 @@ TAB_DISPLAY_NAMES = {
     'curl': 'curl',
     'zulip-send': 'zulip-send',
 
+    'web': 'Web',
+    'desktop': 'Desktop',
+    'mobile': 'Mobile',
+
     'cloud': 'HipChat Cloud',
     'server': 'HipChat Server or Data Center',
     'stride': 'Stride',