I think the step should be
1. have a personal meeting with direct manager/supervisor. Tell him you wanna resign. probably he will ask why. then u tell him got better offer bla bla bla or homesick and so on.... he usually will brain wash you, this is natural manager skill... NEVER disclose where you going.

2. Submit resign letter then CC HR like what phoenix mention. in the letter should have date as of today. then in the letter "as required by company policies, my last day reporting to work will be on <date after 3months of notice>. During this period, I will ensure transition run smoothly to my successor" you rearrage the words la... seems crappy abit. last line should thanks manager for the mentorship and guidance and oppurtunity given bla bla bla

3. wait and goyang kaki. always arrange and maintain good relationship with ur manager or collegue even though u hate them. you can always talk to your manager say this is what i have transition to who who who and what u going to teach next prior leaving. this to show u still loyal to the company. so next time u wanna come back still can.....

hope this help