This is easy, there is only 4 types of cadences you need to be aware of, 5-1(perfect), 4-1(plagal), 1-5(imperfect) or 5-to anything other than 1 (interupted). Listen to the radio, does'nt matter whether it is pop music or classical, Nirvana to Beethoven. Listen listen listen analytically. What chords does the artist use to end their piece? Do you know what a chord is? Do you understand diatonic chord progressions? (MmmMMmm) Do you have a friend who can play some chords on piano or guitar? This will help you, once you get use to identifying certain chordal sounds it becomes easier. R&R typically uses 1451 or 1645. Just identify cadences with what you know and understand, its not rocket science.