In poetry, anaphora is typically defined as the repetition of a word or group of words at the beginning of lines. It is classified as a kind of refrain. In terms of grammar, anaphora is typically defined as the use of a word that refers to or replaces a word that appeared earlier in the sentence in order to avoid repetition. So, the first kind of anaphora is actually repetition while the second kind is the use of a different word for another word so as to avoid repetition.

I suspect that, because you are studying poetry, you are in need of an example of the first sort. We see this first type of anaphora in the poem with the repetition of the very first phrase: "I will arise and go now," which appears on line 1 and on line 9. This phrase helps to establish the pace of the poem—which is fairly languorous—through its use of the long vowel sounds in the words I, arise, go, and now. These sounds take longer to say, and we tend to draw them out more than we do short vowel sounds like the "a" sound in cat or the "i" sound in pit.