SFTP access to sub sites on multisite

I’d like to move a few of my single sites, which are presently hosted elsewhere, onto a multisite set-up at bazzadonboy.co.uk. Everything seems pretty straightforward but I can’t work out how to access any sub sites on the network via SFTP.
I have only used Multisite once before and in Filezilla the sub-sites showed up as sub folders at the top of the main site.
Can you advise on this please?