How do I make my other Pentax lenses work with this?

I'm very interested in the Pentax K100D digital SLR camera. I have used Pentax 35mm cameras most of my life and have a few nice lenses I'd like to use. According to all the information I've read about this camera, my bayonnet K mount lenses should work with it. However, I took my lenses to my local camera store to try them out. The lady was very knowledgable and we tried the lenses. They fit alright but the camera wouldn't allow you to take a picture with the lenses. The AV just flashed on and off and wouldn't take a pic. She still seemed to think my lenses would work, she just didn't know how to do it. My lenses are 25-30 years old, but nice. One is a Pentax 28mm wide angle lense, and the other is a Tamron 85-210mm telephoto with macro. They both work on the SLR 35mm cameras. Of course they would both be non-auto focus but can they work with the K100D? Any answers?
thank you,
Steve Allen

The lenses should work with the camera. But they will be completely manual. So my guess is that the camera store lady forgot to turn the camera to fully manual mode. For example, it would not work in aperture priority or other half-manual mode.

You need to adjust the custom settings in the menu to allow use of the aperture ring with your lens. Then put camera in manual mode. Using the AE-L button on the camera will then set the correct exposure.