how to enable wifi without network router?

I’ve a problem with internet for some weeks.
So I want to use my rasp to hear music but it is normally connected with ethernet wire.
But I want to use my phone’s internet connexion.
I’ve to enable wifi connexion in volumio but I can’t use my network.
How to enable wifi and select my phone?
My phone will share connexion via wifi.

I’m not quite sure what you mean. Can you clarify what you want to achieve exactly, and which parts are working and which are not?

Distilling from the little info, I assume it is like this: your Volumio is connected to your router with ethernet. Your phone connects wireless to this router too. Something is not working, therefore you want to connect Volumio to your phone’s hotspot.

Case 1: router has no internet. This is fine, Volumio still works and you can control it via your phone over wifi. Just streaming services won’t work, and you want to share your mobile internet for it. In that case, manually configure the wireless network in Volumio’s network settings (hotspot does not have to be enabled yet). Unplug the ethernet cable, enable the hotspot on your phone and restart Volumio.

Case 2: router does not work. Unplug the ethernet cable and reboot Volumio. It will automatically start a hotspot to configure Volumio. You can either use this hotspot to connect to Volumio for the time being (without streaming services). Or, similar to Case 1, you can manually configure your phone’s hotspot. Restart Volumio, enable the hotspot, and it should connect to your phone.

I’clarify my problem:
Normally, my rasp is connected to my router via ethernet connexion. Wifi on the rasp is disabled.
But I’ve currently a problem with my DSL connexion.
I’ve no internet connexion for 2 months…And it’s impossible to use the router without an internet connexion: I’m french, and I’m using a “Internet Box”.
So, I’m using the wifi share connexion option of my OnePlus phone.
But the problem for me is that I can’t activate wifi on my rasp to use the share connexion of my phone because I’ve no acces to the rasp!
So, is it possible to access and activate wifi on the rasp, without using my router but via the internet share of my phone?
Can I activate it by using a keyboard directly connected to rhe rasp?
Another solution?

If the Pi has no connection but wifi is enabled, it should make its own hotspot (by default called “Volumio”).

Connect your phone to that (default password is “volumio2”) and the web UI should pop up in the phone’s internet browser. You can then either use that as-is to control things or use the access to set everything up. However if you’re trying to connect to the phone hotspot, then you may need to use another wifi-enabled device to make that connection unless your phone can support both a wifi hotspot and a seperate wifi connection.

The problem is that wifi is not enabled…
I’ll format my sd card, il’ll be easier!