Pre-filled input fields with placeholder/default value

Pre-filled input fields with placeholder/default value

I do have a custom module in Zoho CRM I am trying to pre-fill a field (mandatory field) of a custom module with a specific value (the field will be overwritten by a autonumber in a second step via workflow later). But at the beginning when a new entry will be created in this module the value in this field should be like "Will be generated automatically". 

How can I achieve this? 

Thanks for help.