The first step to creating a Find is selecting the Form the Find will be based on.
This is done by clicking Find and selecting the Form from the popup menu.
You should select a Form appropriate to your search. Since the fields available for defining the search criteria that make up the search condition are determined by what Form the Find is constructed on, you should make sure that the Form you base your Find on contains the Fields you wish to search by.
Once you have selected a Form, you can define the search logic used in the Find.