Press the Wide icon
You will be presented with the screen below
Confirm the Batter and click on the Dismissal type. Select 'Stumped'
If you have pre-selected the Wicket-keeper, their name will appear as the Fielder name. If it wasn't the Wicket-keeper that stumped the batter, then you can choose the fielder's name from the drop-down list
Confirm the wicket details by pressing the Tick