Like other non-Atheros WLAN adapters, firmware must be loaded in order to
make Intel WLAN adapters functioning. Though theoretically it's possible to
install such firmware on Trisquel, there's no free/libre firmware for Intel
WLAN cards. What's more, newer Intel WLAN cards (Centrino series) require ME
to function.
If you can replace it with an ath5k or ath9k, it's the best.
If you can't replace it, e.g. whitelist restrictions, try to flash coreboot
to remove the restrictions.
If your computer has Boot Guard, then you'll have to use a USB ath9k-htc.