Adding Prelims

[Wee Bob]

I'm aware this is a stupid question, but how do you add pre-lims for events?

I'm playing a Strikeforce game, but have had to cancel my prelims for one of my shows as I had 'more than six main card matches' - I'd presumed that as fans expected those fights to be prelims they were. I can't see how to add a fight as a preliminary fight to prevent this.

I know it's a dumb question, but I'd appreciate any help!