At this point you should have some idea of what applications will contain, but let's go over some basics.
They will be asking for your name. If you go by another name than listed on your documents, I would add it into preferred name. You will need you date of birth, your cumliative GPA (all four years), your email (one you will actually check), your current address, cell phone number, gender based questions, your family information, citizenship, ethnicity, and more.
Every college is different and every application looks different. If you only plan on apply to 1-3 colleges, I would reccomend using their individual applications. Once you hit four or more that is when I would reccomend common app.
Let's take a look at what the current Fall 2023 Application looks like for SIUE
Now let's dive into Common App