1. Navigate to Parent App which is the Customer App.
2. Select Relationship.
3. Click Add Relation.
4. Select Parent/Child for Relation Type.
5. For the Child App, select Customer Address.
6. Click Save.

Since the Child App must be sub App, thus the records cannot be directly accessed. You can access this sub App through its parent App only. In this case, you will have to access the Invoice App in order to view Items.

Set Field Layout for Relationship

Once you have set up the relationship between the Apps, the fields will be available for your selections and can be displayed in Field Layout for both types of relationships. The available columns for users can also be set differently based on their roles.

For example, for Invoice App which has a parent-child relashionship with Invoice Item App, you can allow Role A to see all fields from Invoice Item App while Role B to see all fields except for the price.

1. Select Field Layout tab

2. Select Role.
3. For layout type, select Detail View. (Relationship will be displayed in Detail view only.)
4. To display the data of the App, simply drag-n-drop the desired Relationship on the left to Add Section on the right. Add both Contacts and Address, the section name will be automatically set to the Relationship name.

5. When finish adding the Relationship, click Edit Column to select the desired display columns.

6. Click Save, then click save again in Field Layout page.
7. When navigate to the Customer App, you will see Relation display. To test, click Add Contact, the      Add Contact window will show up.

Note: If the records are added from the Parent App, Field Lookup will be read-only. You will see the new relation record added.