I would recommend looking into cognitive poetics. Peter Stockwell is one of the key authors on this approach. You can find some of his publications here on ResearchGate.
I think, first off, you need to determine what you wish to analyze. Your question points to "narratives" and "interviews." Do you have a specific writer or genre in mind? If you narrow down the topic, that would be easier to get help.
I think that would be fruitful for you to take either a narratological/thematic approach or a historical one. Each has its own advantages and disadvantages but you should choose which one is of more interest to you -- given your field of study.
A narratological approach is mainly concerned with the aesthetic value of a text in itself; it deals with the structure of a narrative in terms of language, style and content whereas a historical approach is mainly concerned with the historical and social roots and/or implications of a given narrative.
For the former approach, you can refer to Russian Formalists (Vladimir Propp's Morphology of the Folktale, 1928 and Mikhail Bakhtin's theories of heteroglossia, dialogism and the chronotope first presented in The Dialogic Imagination 1975). For the latter approach, you can refer to New Historicists (Stephen Greenblatt's The Greenblatt Reader, 2005 and Catherine Gallagher's Practicing New Historicism With Stephen Greenblatt, 2005).
I am conducting event ethnography, in one of the event i am analysing the address of speaker who frequently uses different couplets. My supervisor asked me for a poetic analysis. What will you recommend?
I would recommend either Stockwell's Introduction to Cognitive Poetics or Gavins' Cognitive Poetics in Practice. A less complicated volume would be Kalaidjian's Understanding Poetry. Here are also some brief introductions in the form of web pages: https://understandpoetry.wordpress.com/lesson-1/
You might benefit from looking at the appropriate work of Ruth Berman and of Deborah Tannen. I would also recommend the latest edition of the introduction to narratology by Mieke Bal (especially the contrast between point of view and focalization).