A most basic solution to track visitors who came to your site after clicking on your Flash banner: If your hosting provider provides you with your web site access stats, you can link your banner to a specific "landing" page on your web site and see how many times that page will be requested.
For advanced ad tracking you might need to use a third-party ad network (such as Google AdWords) or ad server software (we recommend a free yet powerful PHPAdsNew / Openads adserver).