Class 2 National Insurance Payment for Employed Work Manually

Hello I was wondering if anyone could help. I'm working on cruise ships so I'm classed as employed. I've been advised to pay for my class 2 NI manually each year and self assessment have given me a 18 digit reference number. I've got to pay for the next 8 years so I can claim my full state pension. When should I pay for the the current year so there are no gaps in my NI. Should it be 2022/23 or 2023/24. Also how do I reference this so HMRC know which year I've paid for if that makes sense? Thank you

Hi 14stringDD Dove,
Your first step would be to write to HMRC to request a liability decision.
Please write to HMRC at the following address:
PT Operations North East England
HM Revenue and Customs
BX9 1AN
Please include the following information in your letter:
•    your full name
•    your National Insurance Number
•    your date of birth
•    the date you left the UK - if applicable
•    your most recent UK address
•    your address abroad – if applicable
•    the type of work you do
•    your company name and address – UK and abroad
•    where your contract is held
•    how often you work in the UK
•    your normal working pattern (the days, weeks or months they regularly work)
Once your liability position has been established, you will be advised of what action you need to take.
Thank you.