How do I File Affidavit in the Family Court?

The FMCA's website has an affidavit template which can be found here.

Remember - short, simple statements that are pure fact, not opinion or speculation or emotion. Number your paragraphs with one incident per paragraph. Any attachments, such as text messages, emails, etc., refer to as 'Annexure A', 'Annexure B' etc. and attach each annexure with numbered pages and a cover page. Also read the rules indicated on the link above.