how do i change my location when using the free vpn

Hi This is currently not possible, but might be added in the future. You need the not free Mozilla VPN for features not included in the free Firefox VPN. The Firefox VPN is merely an HTTPS Proxy: Uses a secure proxy tunnel (TLS).

Starting in Fx 151.0 you should be able to change location to Canada, France, Germany, United Kingdom, United States which is also where the built-in VPN has been rolled out. Fx 152.0 may be when it is rolled out in Australia.