Applications
Applications will be your first connection between you and the company you want to intern at. It's important to craft a good application since the hiring team will be reading it if they decide to interview you.
How To Apply Efficiently?
Obviously you can go with the manual way of applying for jobs and keeping track of your applications with a spreadsheet. (It's how I landed every job I've ever had). There are other ways to apply automatically or simplify the process of applying to companies using AI. (Note some of these services may require a fee or only offer limited amount of applications in a day.)
Looking Over the Position
It's always a good idea to look over the internship position before you apply to make sure you have the technical skills to fulfill the position and if the company culture is a good fit for you. (Don't worry if you don't feel like you fulfill all the qualifications. It's still a good idea to apply if you feel like you can do the internship/job.)