Hi ​@love tingting,

Thank you for reaching out to the Docusign Community.  

You can find the option of setting up a custom validation configuration for your fields as part of the Field Properties menu, located at the right side of the screen after dropping your field or clicking on the field to edit. An alternative to this method would be adding the validation setup as part of your Custom Field’s settings in Settings>Document Custom Fields. For more details on this topic, see:

Validation Options for Text Fields

Note: Some advanced features and options are supported only in certain Docusign plans. Your account plan might not support some of the options discussed in this help topic. Contact your account administrator for more information about which options are available for your account. Or, visit our Plans and Pricing web page for more details on the features included with your plan. 

Compare eSignature plans & pricing 

Feel free to let us know if you need further assistance with this. 

Best regards,

Alejandro R. | Docusign Community Moderator  

Please click "Best Answer" below if you find my reply to be a valid solution to your issue!