---
schema_version: "1"
id: 67a1e8c6e2c61f44250098f83176ee4a3418ed80972bef85cf9e070f580e0e3c
title: Assign Attributes to a Custom Data Source
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/mktg/264-0-0/mc_cab_assign_attributes_to_a_custom_data_source.md
canonical_url: https://help.salesforce.com/s/articleView?id=mktg.mc_cab_assign_attributes_to_a_custom_data_source.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: 5b0f2405646d98c7c93039578805e15cdf603ce46b51b688207872f2fcd39914
description: Follow these steps to assign an attribute to a custom data source in Contact Builder.
products:
  - Marketing
  - Marketing Cloud Engagement
release: "264"
---
# Assign Attributes to a Custom Data Source

Follow these steps to assign an attribute to a custom data source in Contact Builder.

1. Click **Data Sources**.
2. Click **Select Data Sources Now**.
    
    ![Note](https://sf-zdocs-cdn-prod.zoominsoftware.com/tdta-mktg-mc_contact_data-264-0-0-production-enus/0e4d875c-8c8c-4be4-8f13-c8278eafbbf9/images/icon_note.png)
    
    Note If you don’t have any unassigned attributes, you don’t see the Select Data Sources Now option.
3. Choose the checkboxes next to the attributes to assign.
    
    ![Note](https://sf-zdocs-cdn-prod.zoominsoftware.com/tdta-mktg-mc_contact_data-264-0-0-production-enus/0e4d875c-8c8c-4be4-8f13-c8278eafbbf9/images/icon_note.png)
    
    Note You can’t assign attributes created from system-created attribute groups.
4. After you click all applicable check boxes, click **Select Data Source**.
5. Select the data source to which you want to assign the attributes.
6. Click **Done**.