How to make a fieldset and add a new extended field in it

Document ID : KB000073159
Last Modified Date : 13/03/2018
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Like for the company name field on a Legal Document form. I would like to add a new extended field, on the external company field set. 
CA Asset Portfolio Management 14.1, 17.x
To create a new extension field (custom field) to display on a legal document form , in the 'External company' blue box:

1. Create a new extension field on the global company configuration, using 'add extension'.  (Note:  Add extension is only available on global configurations.)
2. On the legal document global configuration, select 'add existing fields' and select (drilldown into) the Company/Company extensions link to find the new company extended field.
3.  Select the new company extended field and it will add it to the legal document form (inside the blue box).