In the Standard Edition of VSP:

1. From the Volunteers pane, edit any volunteer.
2. In the profile, click the "Edit custom fields..." button that you will see in the lower left portion of the window.
3. A new window will open and in the lower left side, click the "Manage fields..." button.

You have different options for custom fields: text, number, date, checkbox, and list of options. Once you create the field it will appear in the main part of the screen. You can drag and drop the custom fields to reorder them on the main screen. When you edit other volunteers, the custom fields that you have defined will be available for them as well.

You can edit an existing custom field by clicking on it in the "Manage fields" area and then clicking "Edit".