XPS 13 (9360) Ubuntu system setup failing

Hi there,

I entered a wrong WiFi password during the initial system setup. I cancelled the action and the system started offering only a very limited guest session.

I'm stuck with that guest session which has no useful permissions. There's no other user available.

How can I fix this? I'd basically just like to restart from scratch as I've done absolutely nothing so far.

Thanks in advance...

Franck