To set a multimedia key, first click on which button you want to assign, then on the right click new action and name it whatever you want, after that at the bottom click advanced edit... then the macro editor should pop up, uncheck the record delay and in the white box press any key in it. For example I press left mouse click, so button 1 should appear. Now at the left box is action on press, it should be button 1-down and button 1-up, so click on button 1-down and at the bottom should appear type and action, then just edit type to multimedia and action to whatever you want, and done. Hope that helps

The "Button 1-down" is being displayed under the left box "Action on Press" correct? Click on the "Button 1-down" then at the bottom will appear another box which allow you to set the type and action for it.