setup/index.md: add yourself, link devices, back up JAMI protocol accounts

Change-Id: I2eeced9391b03e614556226749c299b63988f7a5

setup/index.md

@@ -36,6 +36,32 @@ To set up multiple SIP accounts, Jami accounts, and JAMS accounts on one or mult
 * [User manual](/user/index.md)
 * [JAMS manual](/jams/index.md)
 
+## Add yourself
+
+```{admonition} Tip
+This is one of the many unique features Jami.
+```
+
+Add yourself as a contact to enable:
+* Peer-to-peer (without a third-party server) file transfers between your devices.
+* Calling your account on other devices if you forget where the device is.
+* Having one account shared in a family or organization to answer calls from shared contacts.
+* Calling yourself to talk with members in the family or organization who are at different locations.
+* Writing notes and lists to yourself that are available on all your devices.
+* Other use cases that are not listed here.
+
+## Link devices
+
+Link devices to use the same JAMI protocol account.
+
+## Back up JAMI protocol accounts
+
+```{important}
+If a JAMI protocol account has no account backup and is removed from all linked devices, the account is unable to be retrieved.
+```
+
+Back up all JAMI protocol accounts.
+
 ## Jami extensions
 
 ![«Image: Extensions»](images/extensions.png "Extensions")