Citing a previously unpublished master’s thesis, can I simply use part of my thesis to apply to a conference?
It sounds like you're rewriting your previous research into a publishable form. That's completely above board and very common. You wouldn't have to cite your masters thesis because the thesis is effectively an earlier draft of this paper.

See this related question, except the OP wants to turn a published paper into a thesis.

See also this related question, where I asked about self-plagiarism in conference talks.