Domains can be transferred between different domain registrars through a special authorisation process designed to prevent accidental transfers and domain theft. To confirm that you want to move your existing domain at another registrar to 1-grid, an authorisation code will be sent to the email address that was originally used to register that domain.
Under normal circumstances, once you have confirmed your intention, and rightful authority, to transfer the domain via the authorisation code mechanism, the transfer will take place within a few days.