To connect you need to first install a FTP client such as Filezilla.
In these FTP clients you need to specify the server address to which to connect. This is
Use your Core account credentials to connect to the server.
Your FTP client software will ask you to verify the certificate. If it mentions ftp.core.uzh.ch and if its issued by the University of Zurich / QuoVadis everything should be fine.
Please be aware that you only have read access to the ftps server (no upload, modification or deletion of files is possible). Also access from within the UZH network is also not possible via FTPS.