Migrate hosts from Spacewalk to Satellite

Hi,
that's the firts time I've setup a new Satellite server. We have a spacewalk installation (managed by a former colleague) and now I'd like to migrate all our RHEL hosts to Satellite.

I performed installation and tried to add only one host and it works. I was reading about Bootstrap script but it needs a host group before run python script.

Anyone has experience with this task?

Regards,
Fabio