Pacific Coast League - Since 1903
"You can see a lot by observing." - Yogi Berra

The league id is a three or four digit number that is very easy to find.
Step One: Navigate to your league home page
Step Two: Once you are on your league home page, look at the URL in you browser's navigation bar. It should look something like this:
http://www.csfbl.com/leagues.asp?leagueid=1041
The four digit number you see at the end of the URL is your league id. So, in the example given, the league id is 1041, which is the league ID of the Pacific Coast League.