There's two ways.
The first way is that you play out your innings in an exhibition match and when you've come to the number of overs that you have (eg 30)or are bowled out you post screenshots of your scorecards(batting stats and stuff) and send them here under your match topic.
The second way works with 10,20 over or 50 over matches.You play out your innings and when you've finished them by getting bowled out or completing 20 overs,you bowl one over to your opponent making sure you bowl outside off-stump and not looking for a wicket.Once completed you save the game and send the game and screens to the forums.
In the first way,your opponent will start a new innings so don't send in your saved game or bowl an over because it will be a waste of time.
Second way,your opponent will use the GamTweak to swop the teams and play out the 19 remaining overs of his innings.
I hope I've made it clear enough,if you don't understand completely then tell me.
Thanks
Auwais