Count Dooku: Battle of Genosis
This level is entirely contained on a small battlefield. You'll see a number of enemy towers spread throughout, and each tower is contained inside a glowing force field. Go into the force field on foot (you can't drive ships or mechs into the force fields) and find the device that has a switch. Go up to that switch and press the button displayed. This will take down the shield.
Now, take down the cannons by attacking them - any attack will do. Just keep doing this for each force field you see. It's a bit tedious, especially for an opening level, but they will get much more interesting.
Count Dooku: Gungan General
This level is all about taking down force fields yet again, but this time it's more complicated. Again, you'll want to flip all the force field switches, but some of the cannons and mechs require special procedures.
If a machine is encompassed in white electricity, find the satellite dish that's sending the white beam. Take out that dish first.
Secondly, if a machine has a purple target on it, it won't respond to normal attacks. For these, hop onto one of the small speeder ships and run through the gold boxes in the middle of the battlefield.
This will charge your ship with torpedoes. Use your attack button to shoot a torpedo when you see a purple cross-hairs icon on screen. The torpedoes will automatically lock onto targets, so don't soot unless you see the cross hairs.
Again, once all the enemy machines are destroyed, you'll see a cutscene and the level will be over.