After establishing relations, you can access related fields from related tables in the View, field selection dialogs and the Expression Builder.
Using the From Table drop-down list in any Available Fields dialog, choose the related table. Related fields are displayed in the format:
relation name.fieldname
This format shows you the relation name (most commonly the name of the related table layout) used to access the related fields.
You can access related fields in the same way from any command dialog that contains an Available Fields list. Add related fields from the related table to the View by right-clicking in the View and selecting Add Columns. Choose the related table from the From Table list and then select the related fields. See Adding a Column to a View.
You can also access related tables in the same way from within the Expression Builder. You can then build expressions using fields from related tables.