Map reading instructions can easily been found on the net even on You Tube for free. Some are better than others. +1 to the stuff from the OS.
I am a map reading instructor in the army and often do some navigation stuff at meets if people want it.
One of the best tips I can give you that often is not mentioned is to learn your paces. The easiest way to do this is to use street lights or known 100m gaps in a 30mph area lights are often only 50m apart. Try counting the strike of only one foot either your right or your left and between the distances that is how far you walk in 100m multiply it or use pace beads or counters to mark every 100m then you should not walk to many extra miles or kilometres
It also comes in handy if later you learn Naismiths rule which will help planning your trips. Keep it simple in the beginning.
I shall start writing an article when I get some time
hopefully to put some bug bears to bed. Navigation is an important skill but if an officer can be taught anyone can
(although most of use still do not trust an officer with a map if we can help it. I normally do the check navigation to make sure)