Help

Hello everyone I am an undergrad student in CS I want to become a Quantitative Researcher so I will be doing a PhD in mathematics. But how do I go about getting internships I have some projects build Iv done a pairs trading project backtested it and I am now paper trading it. I also have a Portfolio Optimizer project done. What else should I do and what books or resources should I look at. Also what would be the process of getting an internship like how hard are the interviews and how technical?