The process in LoadUIWeb is to:
Record your scenario
Go back and introduce dynamic data to certain points of the recording
Verify that the dynamic data works and has an impact on server responses
In your case, you've gotten through the first step.
To move through to the next step, you can either use the
Parameterization Wizard (if you're using LoadUIWeb Pro) or
create variables one at a time (the free version).
Once you introduce dynamic data (like for instance usernames and passwords),
verify the scenario and then run a small stepwise load test to ensure that the data works for your situation.
