Unlike InDesign, Word has a character-spacing adjustment (Format font dialogue box, character-spacing tab) but no hword-spacing tool. The easiest for you is probably to use find and Replace to replace all your single spaces with number of spaces you would like. Press Ctrl+H to open the dialogue, type one space in the Find box and two, three or whatever in the Replace with box. You won't see any marks in the boxes, but the cursor will move. Alt+A will replace all, or just click on the Replace all button.

Enjoy
Ulo