How do I make an affidavit?

I have to make an affidavit to the family court Gloucester and Cheltenham with regard to my efforts to contact the bith father of my two step daughters under requirements S.52 (1) mof the Adoption and Childrens Act 2002 -so that the court can consider dispensing with birth father's consent to adoption. He is a Thai national living in Thailand who I contacted by telephone and sent the consent to adopt forms with an addressed envelope by recorded mail.