[Koha] Athena to Koha

Good afternoon from Fiji May I ask if anyone has done a migration from Athena 9.2 to the Koha??? If yes, then is there a documentation of the steps used??? Also, is there a PDF or webpage I can view to help me in doing cosmetic changes to the Koha site and the OPAC??? In addition, is there a list of all the features of Koha??? Sorry about asking so many questions but could anyone help please. Regards.