When sending information via API, you may want some fields to be user specific.  This would mean that the fields being passed are associated with the user instead of the lead, list, campaign, etc.  The system can add custom fields specific to a user and the values can be added via Integration.  We can add up to 10 custom fields.

From the Dashboard, click on Account and select Users from the drop down.

Under Show Users, click  Action button and select Settings from the drop down.

Under Credentials Tab, scroll down to Custom Fields

Click on Add Custom Field and enter the value. 

Click on Apply Changes.

To Add information to these Fields, you need to map them through the Adaptor API.