If you have a webcam that needs some module (driver) that it is not in Fedora kernel then you usually need to compile it manually. Fedora doesn't include any modules that aren't in upstream kernel. Livna repository has some modules for some webcams. But if you have a webcam like mine that uses uvcvideo module which isn't in livna repo then only solution is to compile it manually.
First step in getting your webcam working is to check if maybe it is working but you don't know it is :)
Install application called cheese with your favorite gui of cli tool. I use yum so here is how I do it:
su - yum install cheese
If you webcam works that is it, if it doesn't work then you need to find out which webcam module you need to install or compile.
Start tool called v4l2-tool, if you don't have it install it. When you start it you will see this:
Click on the last tab labeled "suggest driver":
Then click on "lsusb output" button:
Now you need to recognize which of all listed usb devices is your webcam. I had only two lines and I recognized microdia as manufacturer of my webcam so I used manufacturer and model ID from that line in my cast that is - 0c45:62c0.
Now you need to enter that info back in main window in "vendor ID" and "product ID" boxes and press suggest driver button:
How you should get the module name and link where to get more info for installing your webcam in Fedora.