After you are done implementing your management system, you are ready for certification by an accredited certification body.
They will send an auditor or audit team to conduct a documentation review (stage 1) and a series of interviews (stage 2) to make sure the management system is working according to the standard. The duration of the certification audit depends on the size of your organization.
Since Instant 27001 can speed up the audit process, some certification bodies are offering a discount on the number of audit days.