Hi, I'm Nathan.
Sorry to hear that you're having trouble with this but I'll do my best to help you, Susie.
This happens when the internal memory/card is actually full. To be able to take more pictures you will need to clear some space.To do that, you connect the camera to the computer via the usb cable, open your computer/explorer folder, and you'll see the camera appear there as a removable memory or drive, open it up, and within the dcim folder you should see all the pictures stored there. You'll need to cut and paste them or drag/drop (while holding the shift key) to another location your computer. If you've already copied them, you can simply delete them from the camera drive or from the camera playback menu.
Do you need more help with this?