See the below thread for importing contacts. May be slightly different file import location on Mac.
Import Contacts - Frequently Asked Questions - eM Client
Generally you go to “Menu / File / Import” using eg: eM Client Windows, and then you can select another (another mail application) to import from at the top part of the window, or choose an exiting (exported file) to manually import into eM Client at the bottom part of the window.
As above should be pretty similar import menu location on the Mac version of eM Client.
