I have an android phone.
How do I run Citrine?
nostr isn't an identity backup. nostr *is* the identity. here's how to create a backup of it!
run your own relay. that's it!
you can do this in a multitude of methods. here's just a few simple examples to get you started.
on Android you can run a relay on your phone: https://github.com/greenart7c3/Citrine
on Windows you can run a relay on your computer: https://github.com/CodyTseng/nostr-relay-tray
on Umbrel/Start9/Mynode you can run a relay on your own server: https://apps.umbrel.com/app/nostr-relay
https://github.com/Start9Labs/nostr-rs-relay-startos
if you want a DIY method, you can run a variety of relays too:
https://github.com/cameri/nostream (i use this one.)
https://github.com/hoytech/strfry
good luck!
Discussion
Install th APK and then configure your clients to use the local relay.
I had install the apk on the android i copied the adress ... Provided by the app ...after i got to amethyst - relays - add relay- paste the adress from the apk - save.... How do i know that it's ok sorry for the noob question
Yes, that's how you do it. How do you know it's safe, well we trust nostr:nprofile1qqs827g8dkd07zjvlhh60csytujgd3l9mz7x807xk3fewge7rwlukxgpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhszrnhwden5te0dehhxtnvdakz7qgswaehxw309ahx7um5wghx6mmd9usjfpck 😂 but we can also review the code that he publishes and build it from source.
Nono not if it's safe .... Just if it's working 
In Amethyst tap this button here and select only your Citrine relay. Make a new note. See if it shows up in your feed. 