The short answer is, practice. Literally, interview more. Apply to jobs you'd never accept an offer from to get the practice. The long answer needs more info

The short answer is, practice. Literally, interview more. Apply to jobs you'd never accept an offer from to get the practice. The long answer needs more information. Why do you think you suck at technical interviews? How do you know that? If the answer is "because I haven't gotten an offer," what makes you think it was the technical portion of the interview you failed? What parts are you not good at? When do you freeze up? Why do you freeze up?