Logic doesn't use VST's... it can use Audio Units (AU).
Make sure you have installed the audio unit version.
Also, where are you looking in Logic?
- Create a software instrument track.
- Click-hold on the empty slot under I/O on the channel strip and choose Komplete instruments from the 3rd party AU list towards the bottom of the pop-up menu.
Do you have the latest updates? What version of Logic 9? 9.1.3? What about your Mac? What processor, etc and version of OSX?