URL: The URL of your pool service. Not the one you plug into your browser, but the one specifically for mining. Any pool service will make this information readily available on the help or getting-started pages. Many have multiple URLs you can choose from, so you can pick the server closest to you. The URL will likely start with the word "stratum."
Port: The port number will also be provided by your pool service. It's usually written immediately following the URL, separated only by a colon and no spaces.
Username: The username you created when you signed up for the pool
Worker name: Before you can mine you have to create a "worker" on your user account on the mining pool. Each worker has a name, either picked by you or assigned automatically by the pool.
Worker password: Similarly, every worker has a password.
When you've created a worker and have all the info you need, go to the folder containing the cgminer.exe file, right-click anywhere and choose to create a new text (.txt) file. In notepad, type the following in, substituting your personal info for the bolded words:
cgminer.exe --scrypt -o url:port -u username.workername -p workerpassword
Here's an example:
Now, hit Save, then go back to the folder and rename the text file you just created to "GPUMiner.bat"--minus the quotation marks. Windows will confirm you want to change the file type. Say Yes.
Again, here's what the end result should look like:
Finally, you can double-click on the .bat file you just created. Cgminer will take it from there, displaying your progress as you mine altcoins.
For a more thorough explanation of cgminer's deep bag of tricks and tips on how to coax better mining performance out of your GPU, check out this excellent advanced guide to Dogecoin mining.
If GPU mining isn't feasible for your PC, you can still mine, though not as quickly. The process is pretty much the same as for the GPU mining process, and you'll still need the same information described above. The main difference is that instead of cgminer, you'll download a program called cpuminer. Just like with cgminer, you'll need to create a batch file by creating a new text file in the cpuminer folder, entering a short script, then renaming it to a .bat file. For cpuminer, your script will look like this:
minerd.exe -o url:port -u username.workername -p workerpassword
And with that, you can use your GPU, CPU, or both to mine Litecoin or most other altcoins. When you start accruing coins in your account, you can visit the mining pool's website and enter an address to have the coins sent to your personal wallet. You can find your wallet's address in the "Receive" tab of the client you downloaded earlier.