Go into setup and see what key(s) you have assigned to speed. If you have not marked a specific hotkey, the you will need to cycle to that force power (using the "next force power" or "previous force power" keys) the hit the "use force" key. You also have to be sure you have enough force mana (red indicator on the lower right of the screen..). Speed doesn't use that much, but if the indicator is all black, or has just a tiny tiny bit of red at the bottom, you'll need to wait for more to build up (soldi red or orange) before it will work (grab a force boost or surge to speed up this process).
To use the power, you should just hit the key and the words "force speed" should appear at the top of the screen (along with an icon of a guy running in the upper right corner of the screen). If it "worked" you'll hear the sound effect and be able to move faster for a short time.
[This message has been edited by Kurgan (edited July 21, 2000).]