You must have registered and be signed in to edit a case.
There are a few ways to select a case for editing.
You may well have a list of cases that you have set up. You can select one of them for editing by clicking Edit from the Case List/Summary page:
A second way to edit the active case is to click Click here to Edit the Details for this Case from the Case List/Summary page:
A third way to edit the active case is to click Click here to Edit the Details for this Case from the Your Questions page:
Having opened a case for editing, you can set the parameters as described in Creating a Case.