i can actually load it and enter the parameters. but i don't know how to start it. i have tried pressing the shutter button, but nothing happens.
What do you mean "nothing happens"
After you set the script settings, you should exit the script menu, but stay in CHDK alt mode. Then when you press the shutter, it should run the script, or produce an error of some kind.
also, i am curious: the installation of chdk told me to lock the memory card. but if the memory card is locked, how can the camera write photos to it?
CHDK causes the firmware to ignore the lock setting. The lock tab doesn't physically prevent writing to the card, it just engages a switch the software reads and decides whether it should consider the card locked.
