Cultural: talk about what was going on in the world at the time the artwork was made that might have influenced the artist to make it. Cultural frame is about context.
Subjective: Talk about what the artist wanted to say through the artwork and how the artwork might make an audience feel. Subjective frame is about emotions and thoughts.
Structural: Describe the art work. Talk about how it's made, the materials used, the medium, the size. Also talk about things like colour, perspective, lines, tones etc. and how this helps convey meaning.
Post Modern: This one's harder. Characteristics of post modernism is appropriation, recontexturalisation, trash aesthetics, found objects, text, irony. The best way I can explain post modernism is that it's about challenging traditional conventions. For example, when talking about Marcel Duchamp' s "L.H.O.O.Q" through the post modern frame you would say how it is an appropriation that uses irony to challenge traditional artistic values.
Hope I helped :)