If it is an integrative literature review, then you can use the the approach described in Whittemore, R., & Knafl, K. (2005). The integrative review: updated methodology. Journal of advanced nursing, 52(5), 546-553.
What I may suggest you for "theming qualitative data" is reading with open mind articles you found. Then, highlight what it's relevant according to your research and themes will naturally appear : if data often occur, you may consider it as a whole theme. The method may be compared to the inductive process in qualitative methodology.
I don't know if it answers to your question but i wish you the best for your dissertation.