To be eligible for permanent residency under this visa, you must meet all of the following requirements at the time of lodging an application:

you must hold a qualifying visa

the nominated position must relate to an occupation listed on the ENSOL.

You must also meet one of the following requirements:

have worked full-time in Australia in the nominated occupation on a Subclass 418, 421, 422, 428, 444, 457 or 461 temporary residence visa for the last two years prior to the visa application being made (including at least the last 12 months with the nominating employer)
have been nominated to fill a position with a base salary of more than AUD250 000 per annum (excluding superannuation or allowances)
have had your skills assessed as suitable by the relevant skills assessing authority and, unless exceptional circumstances apply, have at least three years full-time work experience in the occupation before the visa application is lodged. A list of assessing bodies can be found in the Employer Nomination Scheme Occupation List (ENSOL).
You must also:

have an employer who is willing to sponsor you for permanent residency
demonstrate that you have the appropriate skills, qualifications and/or experience to fill the position
meet any mandatory licensing, registration or professional membership requirements which allow you to work unsupervised and without further training
be under 45 years of age
provide a letter of appointment or a contract signed by both the employer and yourself
have vocational English language ability.