do you mean how do you collapse them so only a piece of the boxes is visible, or do you mean how do you make the entire box take up less space on the screen?
If it's the former, you have to click one of the bubble-looking buttons on the top-right of each box.
If it's the latter, you would have to increase the resolution you're playing the game at. For example, if you're currently playing it at 800x600 dimensions, try upping it to 1024x768. Also, playing at fullscreen instead of windowed mode should help. This, of course, is assuming you aren't already at the max resolution your monitor and video card will handle... If that's the case, you'd have to upgrade those first.