Typically, the account owner on the family plan simply needs to request a port out pin which you then provide to Visible to establish an account with them. Best to check with Verizon concerning how that port out request needs to be initiated and by whom. Despite being Visible by Verizon they are separate business entities so it's no different than transferring to any other carrier unaffiliated with Verizon.
You then simply signup for a Visible account provide the port out pin and number and once you complete activation the Verizon line will be canceled - the Verizon family plan pricing will then change to reflect one less line (if multi-line discounts were involved).
You actually don't need to port immediately, sign up get a new line, and you can port in once your comfortable with Visible. Use either the trial and/or grab someones referral code and save $20 off your 1st month of service. Sometimes it's adavantageous to defer porting to later in the Verizon billing cycle.
See: https://www.visible.com/help/how-do-i-transfer-port-my-number-to-visible
Follow the porting instructions to the letter - occasionally some have missed a step or two and wind up stuck in porting limbo.
Good luck!
