Go to Scoring>Match Details/Teams.
This will bring up the match information and allow you to edit:
You can change a match official by left clicking on them and choose the correct official from the drop down list and select Save.
If you notice the officials details are incorrect you can change then by selecting Edit next to their name.
Once changed, press Save.
If the official is not on the drop down list you can add them by left clicking Add.
The boxes marked in Red are compulsory fields. Once entered, press Save.