If you need to access services on behalf of Operators or Lessors, then you need to register for an individual account and be added to the Operator / Lessor account. At present, you cannot be linked to multiple Operators or Lessors so if you need to work simultaneously on behalf of multiple operators you will need multiple accounts.
Alternatively, if you access services on your own behalf, you will require your own marketplace account, subject to compliance checks being completed and approved.