When presented with one of these types of 'selection' fields, you can choose multiple options.
To do this, hold down the Ctrl key (or Cmd key, if on a Mac) and click the desired options. You can also choose an option, hold down the Shift key, and choose another option to bulk-select all options in-between the two choices.
NOTE: We've seen scenarios where a browser extension can cause this functionality to become disabled. So, if this isn't working properly for you, be sure to check that you don't have a browser extension installed that is blocking it.