1. Graduate nursing school.
1b. While in nursing school, see if you can get a job as a mental health tech or a CNA/tech on a psych unit. That will give you related experience and a chance to network. Plus you'll get to see what psych nursing is like.
2. Pass the NCLEX.
3. Look for psych jobs. There are new grad residencies in psych--they're not as common as the others but they do exist. Some facilities take a chance on new grads in pysch, but be warned that there is a steep learning curve. This is where getting prior experience as a tech can be an asset.
4. While it definitely can't hurt, working med-surg first is NOT required for a successful psych career. You are going to learn the basics of nursing such as organization, delegation, time management, med administration, etc. no matter where you work your first year. You can keep up on the medical side through CEUs and education. Most importantly, since psych patients do not check their medical issues at the door when they're admitted, you'll be working with both psych and medical issues from day 1, so you'll learn a lot from there. Don't fall into the trap of thinking that you'll never use your medical nursing assessment
skills in psych--you'll use them more than you think.
Of course, land on a psych-medical unit (a cross between a med-surg floor and a psych unit: patients are more medically acute than you'd find on a psych unit, and more psychiatrically acute than you'd find on a medical unit) and you score the best of both worlds.
Hope this helps.