You have a three piece bottom bracket. You'll need Park Tools HCW-4 or similar to remove the fixed cup, and HCW-5 for the lock ring on the adjustable cup, and a suitable tool (a large crescent wrench often works) depending on the configuration of the adjustable cup. The pins on HCW-4 will fit some.

Look in Sheldon Brown's site for more tools and tips. Pay attention to the left-hand threading on the fixed cup, and you may need penetrating oil, heat, and/or mallet impact on wrench to free it.

Note that it's not always strictly necessary to remove the fixed cup. If you can clean it from the adjustable side, and inspect it well enough, you can just leave it.