Answer:
Typically, you examine it closely. You read it to try to grasp the feeling or thought behind it. You can read it out loud to listen to the meter or the sound, which in some poetry can be very important. You look at the words individually, and how they relate to the whole, and try to understand why a poet used the words he or she chose, and look at grammatical conventions and try to understand why they were followed or ignored in certain cases. Was a word chosen to make a rhyme, or is that really the best word? Is the capitalization significant? What is the poem saying to you as a reader?
Not all poetry will appeal to every reader... but there is a lot of poetry out there, and if you find some that you appreciate, reading it often helps you learn more about the art, and understand and appreciate more varied entries in the genre.