All of the information concerning the CIL requirement and its logistics are contained on the CIL website.
In the CIL Lab throughout Fall and Spring semesters, Short Courses on the CIL subjects and the basics of taking a CIL test will be given. These presentations are announced under Short Courses on the CIL website.
Most students prepare for the tests by reviewing the online tutorials, which contain information about all skills and concepts necessary to pass the tests.
You may also email a member of the CIL staff at email@example.com and ask questions or come by the CIL lab in ESLC 131 and ask a consultant.
If you've already taken a test and did not pass, you can see what sections you did poorly on (for Concept Tests) and exactly what you missed (for Performance Tests) from within the testing program, iNetTest. This is probably the best way to study after already taking a test, as you can focus your studying effort on the areas in which you did the worst. Just login, find your test, and use the "View Results" button to see the scoring breakdown.