What steps do I need to install a new circuit panel box

Step 1: Find the names of a couple of reputable electricians.
Step 2: Pick up the phone and call said electricians.
Step 3: Get quotes from said electricians.
Step 4: Choose the one you feel most comfortable with and have them do the job.

Roughly, after you determine The Panel you need and correct Service wires.
Look at EVERY Wire in the panel. Identify all wires on all breakers. Use white tape to identify any neutrals and green tape for grounds that are not clearly Identified.
Watch for multi-Circuits and be sure they are on opposite Phases.
Then Take particular Notice to any conductors Not on Neutrals, Grounds or Breakers. Like Low Voltage Control wiring for AC, Etc..
All will need to be done by a Qualified Electrician, Injury or Death could result.

Calling a licensed electrician is the 1st step. 2nd Step is to let them do the job.