Usually, you would want to run a test that simulates a complex test case. First, you create the complex functional test and then simulate multiple users performing actions against your server. Here is the instruction on how to create a new test from a functional test:
Right-click a test case and select Create Load Test.
In the appeared dialog, specify the name of the load test and click OK.
Right-click the Performance Tests node and select Create Load Test, or click
in the toolbar.In the New Load Test dialog, switch to the Manual tab and select the Test case option.
Enter the name of the new test and select the test case.
Click OK.
ReadyAPI will create a load test based on the selected test case.