actually I think I did everything right. I locked the card and now I see the CHDK logo. however it must not be 'turned on' because the lens won't extend.
When CHDK loads, it does so in playback mode only. There is a long history that I won't go into here behind that design choice. Press the shutter button (or playback button) to switch to shooting mode and extend the lens.
Did pressing the PRINT button activate the CHDK <ALT> mode.