If you want to make your field require an input, enter the template editor of your template.

Locate the field you wish to make mandatory and click on the pencil icon.
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 Once the element details appear click the Yes radio button under Mandatory Field.
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Once selected click on Save changes.  The field will have a red asterisk next to it indicating it is mandatory.
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The client will not be able to submit their engagement unless this field in the template is filled in with data.
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