You normally generate fixtures while you are creating the competition. If you need to add to the fixture or change it, you can do this from within the competiton.
From Competitions, select Manage Competitions.
Find your competition and click on the name.
Click Regenerate Fixtures.
Enter the number of rounds for which you want to create the fixture. Click Regenerate Fixtures.
A warning message will display. Click Yes, proceed.
You can view the fixture on the Fixtures/Results tab.