How to setup wifi on (after) a new hassio installation?

I have a clean installation a Hassio 0.77.3 on Raspberry PI
It work wired to my network.
I tried to setup the wifi connection, but didn’t succeed

Connected on SSH (puTTY), I created wpa_supplicant.conf and interfaces files, with the correct content.
But when I reboot the raspi, all the files have disapeared !

I search on the net, but no info on how to setup the wifi.
Have anymore some clue or a link to a webpage with clear (and up to date) explanations ?

fyi : during the initial setup of the hassio, I had the USB stick with files to configure wifi… but it did not work :frowning:
Thanks in advance