as far as I know you need to either work with HP or a partner in order to do a migration. From previous information migration will only move some things but not the real things like rules, forms, templates and workflows etc. So migration is not really a migration and will require a lot of manual rework into the new tool.
Discuss with your HP rep for the official line but it may be similar to this.
actually i have no information about the migration tool, if the migration you want to execute will only deal with ticket data (incident, Service call, changes ..) you can perform this with just bulk exports from Service Desk to spread sheets and then using connect it to import this data back to service manager, while taking into consideration that the concept of workorders have been removed and tasks has replaced it. As for the configurations, you will need to reconfigure since this the automation is done differently. hope this helps,
The Migration Reports and tools for SD 4.5 have not yet been released. They are scheduled to be released with the 7.01 release of Service Manager, which should be out approximately 90 days after the release of 7.00. HP has been conducting a beta of the tools with multiple customers--I haven't heard if it is complete or about the results.
The data migration utilities will be Connect-It based. Business rules (UI and DB rules) cannot be transfered by the migration utilities and will need to be evaluated and reimplemented using Service Manager 7 methods and utilities.