To get a good grasp on meter, try to identify the type used in a rather obvious example. Shakespeare's love sonnets are famously written in iambic pentameter. Mark on top of the words the weak-strong stresses (- / ). Most pop songs use a very strong meter in the lyrics, which acts as the song's beat. After that concept is mastered, move on to a more complex poem, such as Keats' "Ode on a Grecian Urn" or Sandburg's "Fog."
Using a more basic type of meter (such as iambic pentameter or dactylic tetrameter), try writing an original poem that follows that style. Don't deviate too much from it yet. Keep each line using consistent feet and meter. Remember that the style doesn't have to be contained within a single word. Rhythm can extend between words, with the weak stress on the last syllable of the word leading to a strong on the next.
Take the newfound knowledge of identification and copying and try exploring more complex combinations. Many poems, especially those written in more recent centuries, are very experimental in the use of meter and feet. Write poems that use these kinds of collections of meters. Try to have them match in some way the message conveyed in the poem. Look at Roethke's "My Papa's Waltz," which slides in and out of meter to convey a message of instability and drunkenness.