Need help in Load runner

Hello guys,

I am totally new with the Load runner. Our client need to do performance testing on one web application. The problem is if number of users (lets say more than 1000) using search functionality same time with the different keywords our server get down and application crashed. The application is for cell phone and accessories related. 

I have no idea how to test this scenario with the Load runner. Any help would be appreciated. I installed 10 days trial version Load runner 11 from the HP website. I am referring tutorials but not getting clear idea.