The Ordnance Survey have put online eight excellent videos on YouTube presented by TV presenter, adventurer and OS champion Steve Backshall which take you through the basics of how to read an OS map and how to use a compass. Here they are.
(You do need to watch some in order, for example "Taking a 6-figure grid reference" refers back to "Taking a 4-figure grid reference" and the three compass ones are really a set.)
WalkLakes recognises that hill walking, or walking in the mountains, is an activity with a danger of personal injury or death.
Participants in these activities should be aware of and accept these risks and be responsible for their own actions.