Using InDesign Scripts:

Step 1 – May not be required

I am assuming the script has already been installed.
Before using a script you “may” need to select something—such as a fraction you want to format properly. Some scripts do not require this step.

Step 2

To invoke the script double-click it in the Scripts panel.

To open panel in CS2 or CS3: Window menu > Automation > Scripts.
To open palette in CS: Window menu > Scripting > Scripts.

Done!

Maybe the script will be finished. Maybe it will open a dialog for you to choose some options. That all depends on the individual script, but that’s all there is to invoking it.