summer internship

I am an undergrad in math and stats with not too much coding experience or quant work experience.. i do not know what kind of quant role i want
I am going to start my MS applied math degree in fall 2021
When is a good time to start applying for summer 2022 internships? and when does the application period begin and end ?
How can i make my application strong for internships? I am already doing coding courses in python and revising math and stats topics from my undergrad curriculum