Add the following CSS in the module advanced custom CSS.

/* START Space out menu items */
selector .et_pb_menu__menu,
selector .et_pb_menu__menu  .et-menu-nav{
  width: 100%;
}
selector .et_pb_menu__menu  .et-menu-nav .et-menu{
    justify-content: space-between;
    width: 100%;
    margin: 0;
}
/* END Space out menu items */ 
Code language: CSS (css)