Do you mean a theoretical framework for your research? If so then you would decide what educational theories are going to be the foundation of your thesis. From there, then you write your justification on what you are using those theories. For your paper, obviously TPACK is going to be one of those theories but you probably will want to use Constructivist theory as well. What is the context that you are studying? TPACK implementation in the classroom? Professional development? Intrinsic motivation to use TPACK for teachers?
It is worth mentioning here that a conceptual and theoretical frameworks are not always used interchangeably but as two separate constructs as espoused in these resource links:
Imenda, S. (2014). Is there a conceptual difference between theoretical and conceptual frameworks? Journal of Social Science, 38, 2, pp. 185-195: https://pdfs.semanticscholar.org/4b40/2748598965cf7618a6a7ba7f416782f27ca2.pdf
Literature reviews, conceptual frameworks, and theoretical frameworks: Terms, functions, and distinctions. Human Resource Development Review, 8, 1, pp. 120-130. : https://www.researchgate.net/profile/Md_Uddin17/post/There_was_a_paper_that_talked_about_the_difference_between_Model_Framework_Theory_in_Business_Management_area_Can_someone_give_me_the_details/attachment/59d6512379197b80779a9c2d/AS%3A506311842713600%401497725558315/download/Rocco%2C+2009.PDF
I agree with Debra that the first step would be to make sure you need to do a conceptual or theoretical framework! If you are going the theoretical framework path, then think about what are the foundations of the development of TPACK. Then think of why TPACK is used; what theories does it support? Answering those two questions should get you started on the right track.