Do you have BT broadband? If not I can't see how it could be legally free if that's what you want- except that the BT showcase channel on freeview sometimes shows a match
As F-F indicates, there are just a few live matches available free of charge throughout the season.
Quote:
"In total, BT Sport will be making 12 UEFA Champions League and 14 UEFA Europa League games free-to-air this season. The games are also shown free-to-air on TV on BT Sport Showcase, which is available on BT TV and Freeview (channel 59)"