I Need Some Info On Moving To The Usa

My name is Ann and i live in Canada, my sweetheart lives in the usa .We want to get married and live in the united states.I have no clue where to look for information or the first step...i heard about a fiance visa from reading these message boards here.Also i have 2 children ages 14 and 12 and i have soul custody and the paperwork.I desperately could use any advice to where to go from here.thank you muchly appreciated.please email me thanks again
Stardust_annm@yahoo.com