Making further Class 3 contributions after a 3 year gap

I applied to pay voluntary class 3 contributions from abroad shortly before I retired 3 years ago and made some payments at that time. I would now like to make further contributions. Do I need to re-apply or can I just make payments using the instructions on the back of the HMRC letter from 2021? I have 23 years of full contributions.

Hi John,
Since you received our letter in 2021, the rates of voluntary National Insurance contributions have increased.
As you are over pension age, you may wish to call The Pension Service on +44 191 2187777 and they will be able to help you further.
Thank you.