In the SAP menu, choose  Tools IDoc Interface/ALE Development BAPI Serialization Serialization Using Business Objects Determine Supported Business Objects (transaction BD105).

Enter all the business object types relevant for serialization.

In the SAP menu, choose  Tools IDoc Interface/ALE Development BAPI Serialization Serialization Using Business Objects Assign Message Type to Business Object (transaction BD104).

Assign the message types relevant for serialization to each business object type.

In Customizing (IMG) activate the serialized distribution in both the sending and receiving systems:

ALE IMG (transaction SALE)

Modeling and Implementing Business Processes

Master Data Distribution

Serialization for Sending and Receiving Data

Serialization Using Business Objects

Execute activities Activate Outbound Business Objects and Activate Inbound Business Objects. Set the Serialization flag for the required business object types.