Before creating a Glide app, you should have a basic Google spreadsheet document containing the rows of data you'd like to display in your app.
The first row should be column names. For example, if you're making an Employee Directory app, your first row could contain column names like
Photo—these are the properties that each of your employees has:
After the first row, every following row should have values in each of those columns; every employee has their own
Photo. It's okay to leave cells empty if, for example, an employee doesn't have a phone number.
Now you're ready to make your first app!