[Koha] Database change/Multiple databases

Hi, When installing Koha, I used MARC21 as my database. Now I would also like to test Unimarc based databases. How would I go about to delete al records in the MARC21 database? and also install the 2nd Unimarc database for another library. Where can I get instrauction on how to do this? Regards and thanks. Renate