arch linux and broadcom

[Linux for blind general discussion]

I got arch on a usb stick.
After booting and using arrow down, then enter, arch came up talking.
But even though there is an ethernet cable, I cannot get on the net.
Never is this a problem with ubuntu or pop os or with fedora.
Anyone aware of a way of getting on the net?
I also have a u s b wireless wifi adaptor, but with arch, not sure what to do.