If you wish for this field to show up in the user postbits, you will likely have to edit the "postbit_legacy" template to add the HTML at the location you want. You will need something like:
Code:
<vb:if condition="$post['fieldXX']">
<dt>Field Description</dt><dd>{vb:raw post.fieldXX}</dd>
</vb:if>
The code in red will pertain to the new field you have created, where "XX" is the field's id and "Field Description" is the text you want to describe the field.