Postponement of Retirement

Can someone please help me? I have been trying to find this answer for 1.5 years and even contacted a retirement specialist with my agency who just sent me articles to read with no answer. If I have met my MRA and have 20 years, I can postpone my retirement with full benefits retained if I request my retirement at age 60 by "SEPARATING FROM THE SERVICE." Can someone please tell me if I decided to do this, how would you separate from service? Do you just RESIGN and then fill out the retirement RI 92-19 60 days before you want your annuity to begin? Or do you actually go into your retirement platform and hit the retirement button and complete the retirement application and retire; then fill out the 92-19 60 days before? Are you retiring or resigning?