If you want to resize an artboard in Illustrator, you can use the following steps:

  1. Choose the artboard you want to resize from the main menu.
  2. Click on the resize button in the bottom left corner of the main window.
  3. In the resizing dialog, you will be asked to choose a size for your new artboard. You can either choose a default size or enter a new size in the box on the right. The default size is usually enough for most purposes, but if you need to make your artboard larger or smaller, then you can change this value later on.