Read poetry written in Iambic Tetrameter to learn the structure of an Iambic Tetrameter poem. Notice that each line has eight syllables and that every other syllable has a beat to it, so that you have eight syllables with four of them stressed or accented.
Listen to the way each line of Iambic Tetrameter sounds by reading it out loud. Listen to the way the syllables are accented as "da DUM da DUM da DUM da DUM" in each line. Think about how the words work to create the sound of the poem.
Write a poem in Iambic Tetrameter. It doesn't have to rhyme, but if you can rhyme if you want to. There is no line length for an Iambic Tetrameter poem, so it can be as short as four lines or as long a book, which is what Herman Melville did when he wrote a book-length poem in Iambic Tetrameter that's called, "Clarel: A Poem and Pilgrimage in the Holy Land."