HTML only allows for one space between characters; to add additional space in a document you must insert a non-breaking space. You can set a preference to automatically add non-breaking spaces in a document.
Select Insert > HTML > Special Characters > Non-Breaking Space.
Press Control+Shift+Spacebar (Windows) or Option+Spacebar (Macintosh).
In the Text category of the Insert bar, click the Characters button and select the Non-Breaking Space icon.