The general process of making an application is to search for potential companies, write a generic CV/Resume, tailor your CV/Resume to each specific application using information you gain from your intelligence gathering, write a specific covering letter for each application finding out who you should be writing to, the follow it up after you have sent it.
The covering letter gets the CV/Resume read. The CV/Resume gets the interview. The interview gets the job. You can fall out of a successful process at any stage!
There are a great many online resources on CV/Resume writing and formatting.
You will need referees who will give you a good reference. If you have completed work experience before or if you have or have had part time employment your previous employers may be prepared to give you a reference. Your academic supervisor or one or two of the members of staff at your academic institution may also give you a reference if you ask. Otherwise friends, work acquaintances or your network again. Really good references are from people in the discipline area that you are applying for an internship in so if you have the choice choose wisely.