http://iscoresports.com/

How do you go back and change something after the game is completed?

Go to Game Manager, select the game, select Pitch by Pitch, then tap on the pitch you want to edit and your choices will come up. You can make missed substitutions, change hits to error, errors to hits, etc. You can not change outs to hits and hits to outs as that can lead to other problems down the road (what if there were now 4 outs in the inning or only two outs because of the change? etc..)

I need to add a stolen base that will change the score.

In order to make a change that is going to change the score, you would have to use Undo back to that point in the game, and then rescore everything after that point. If all you care about is the Stolen Base statistic and the Run Scored for the player, you can go to Game Manager, select the game, select Batting Stats for the team with that player on it, then tap the Stolen Bases value for the player and manually increase it by 1. Tap the Runs value for the player, and manually increase that by 1 as well.