1- create an Attribute Group in Data Designer for your SMS CustomActivity in order to facilitate data biding in Journey builder (more on that in Step 8) in this example I will name the Attribute group "SMSCustomActivity"
2- Create a Data extension where you pull required information for your SMS sending
(Name, mobileNumber ...)
3- connect The new data extension with Your contact Data model (Contact Key)
4- save everything
5- populate your DE with the users with valid MobileNumber
6- In journey builder, you can have multiple instances of your custom activity,
7- each one with a different text that you can edit and save. (Marketing Cloud is able to save your custom activity Payload)
-8 Than it's up to you to send Data to your custom activity server in the following format (Notice the Attribute Group name use)
9- every contact entrering your Journey will be identified in the SMSCustomActivity Attribute Group and his data will be sent to your custom activity endpoint.
Important: The SMSCustomActivity Attribute group is to simplify data access from Journey builder, Make sure to populate your Data extension with an Automation or with a couple of records manually for testing.
You can always access contact data the way below, but for clarity, I suggest to have Attribute groups with specific use-cases.