To view your wager history you will want to be on the desktop site. (You will not be able to view wagers placed before today from the app or mobile site. You can reach the desktop site from a mobile device by tapping More, then Go to Desktop.)
You will find your wager history under Account, then My Bets.
You can adjust the viewable time frame by clicking the blue calendar icons or by clicking the buttons below to show today, yesterday, last week, and last month.
You can also filter the results by track and wager type.