Without going a lot into detail, let us answer this question generally. If you want a Computer Science Internship, here are some of the measures you need to take:
1. Apply for the Summer Internships - The first thing, of course, includes you applying for the position. You need to pick any of the Companies you are interested in and apply for the position by filling out an application form or some other procedure.
2. Appear for the Interview - Some Companies hire you through an Interview, and some like to do multiple. There are different rounds that you need to clear.
3. Wait to hear back from the Company.
4. Hired? Whoo! - Well, if everything goes well, you can get a final call from the Company that you have got the Internships. That’s great! You can easily join now.