1) Go to the Addl Fields Tab.
2) Enter the field yo want to use. By Default its set to FName to show the first name of the children. You can choose any field from the dropdown. You can also combine multiple fields for example FName & " " & HebrewClass will show the first name a space and the Hebrew class.
3) Here you enter what text you want between the fields. The default is a comma. So it will come out Moshe, Yaakov And Chaim
4) Is for the last connection if you want to put the word and or something else before the last child.
5) Then you click on add fields. You can add multiple fields. When merging the fields the first field will be named Comma, the second A, the third B and so on.
6) To clear all fields click on the clear fields button.
Remember to chose Change Fields to allow to add the field created to the document.