The reference citation should look like the following: Name v. Name, Case Number (Court Abbreviation Year).
So this citation would be: Illinois v. Lidster, 540 U.S. 419 (U.S. 2004). In text, you would use (Lidster, 2004).
Here's where you find those pieces on your LEXIS document.:
Did you find your case somewhere other than Lexis?? Contact Becky for help finding the pieces you can't locate.