I would be happy to lend my expertise to you for this question. I am going to assume that you are using some form of a windows operating system on your computer. I could support Linux related questions, but don't work with apple. So with that said most of the time I recommend installing your drivers from a disk. In case you don't know what a driver is I will explain it to you. A driver is software designed to control hardware. Many times after plugging in a hardware device like a logitech quickcam webcam windows automatically installs some stock drivers for that device. So if you are using the device to video chat on skype that might be enough. Although if you want to install the logitech software specific to your webcam. There are two ways you can do this either by disc, or by download from the internet.
From there you would click on the picture that looks like your webcam. If you don't find your quickcam on the first page, click the still can't find your device on the bottom right of the page for another page of webcams to choose from. Those are the older models. Once you selected what type of cam choose the downloads tab just above the picture of your camera. after that choose which Operating system you have(Xp, vista, or 7), then which language(probably English), & then 32 or 64 bit. After this you can select the download software button. Once downloaded you want to right click on the installer and select run as administrator. make sure to check I accept the terms...click next a few times then finish up. Now when your computer boots you will have a little mini camera in your bottom right system tray that will allow you to take video, or pictures as you will. Some of the software comes with logitech vid. It is like skype, but only for use with logitech cams on both sides. I wish you the best of luck in your ongoing computer adventures.