Adrian and jruberto have mentioned some things you could do.
I would like to add some general information.
The first thing you want to know is what the goal for your load tests should be. You should ask your group's lead what she wants to be tested, or what information she wants to have. Maybe she is interested in some specific component or web service. Maybe she wants the hole system to be load tested.
If the goal is to test the complete system, it is useful to first determine a profile of your application. If you have some kind of monitoring built into your application, you can use this to determine which components or services are used how often, and at which time of day.
If there is no monitoring information, you can also estimate the usage of each component over time. E.g. for the number of users: At 7:00 there are 20 users working with the application. From 7:00 to 12:00 the number of users increase to 350 users. From 12:00 to 16:00 the number of users stays at 350, before decreasing to about 20 users at 22:00, where it stays until the next morning.
You do this also for each component or service or business workflow of your application, or for the most important ones. E.g. at 7:00 there are 30 workflows of type X per hour. Between 7:00 and 13:00 the number increases to 500 workflows per hour and so forth.
If you have this information, you can determine a load profile which is similar to production load. You design your tests accordingly. You can for example test increasing load starting at minimum production load and ending at maximum production load over 3 hours.
If a higher load is expected than is currently visible in production, you have to increase your load profile accordingly.
Generally, with load testing you want to know how the system or component behaves under load / how it handles this load. Mostly this is done using increasing load, or using a load profile which is similar to expected production load over a day as explained above (with increasing and decreasing load).
You increase the load up to the specified load the system or component was built to handle.
You can also increase the load beyond the specifications of the component or system for short periods of time, e.g. 10 minutes. This is called stress testing.
I hope this helps.