If for any reason you need to update the timeslots you have allocated in your fixture, this can be done by simply modifying the fixture.
Simply navigate to your chosen league and select Modify > Update/Extend. Here you will have the opportunity to select the rounds you would like to update and the new timeslots you would like to add.
By selecting 'See preview' you will be able to see all proposed changes before saving the changes to your fixture.