Hi dorothyp,
For a field to be added to a screen as a checkbox, the field must be a Yes/No field. Once you have added the Yes/No field to the table, you can locate it by name in the screen designer on the left hand side and drag it onto the screen.
If you do not see the field after adding it to the table, perhaps you added the field to the wrong table. All screens have a base table and only fields from this base table will appear in the list of fields when customizing said screen. For example, if you are customizing a copy of the CRM_EditCustomer screen, you will only be able to select fields from the Customer table (not the Contacts table).
Depending on what you are trying to accomplish, it might be worth noting that that Contacts table already contains an indicator of the QuickBooks main and alt contacts in the field SpecialType. If the contact is the main contact, this field will have a value of “Contact”. If the contact is the alt contact, this field will have a value of “AltContact”. This information is readily displayed on the Customer and Contacts List Screen under the field heading Rep / Type / Title.
If you’re fairly new to Method customization, it may be worth your time to watch our customization webinars. They are a little bit dated, but the information that they provide is still valid and they do a decent job of introducing some common customization concepts.
I hope this helps and please don’t hesitate to post back if you have any follow up questions.
-Audisho