The basic (but not the easiest) way to run a macro goes as follows:

  1. In LibreOffice Writer, open the menu Tools > Macros > Run macros…
  2. In the Library dropdown tree, make sure the library is selected
  3. In the Macro Name list, scroll down and select the macro called Reformat
  4. Click on the Run button

If the whole text of the page is selected, it’s the sign that the macro is done reformatting the one-pager!