You can simply use your own name during sign up when being asked to provide a company name. Please be aware that we do not allow registration with a free email address (e.g. Gmail, Outlook) so you will need a domain that you use for work and an email address belonging to that domain.
If you're a freelancer working temporarily for a company that uses Luna, please ask a company admin at the organisation you're working for to provide you with an invite to their company. They can delete your account for you following your commitment.