Can you directly import a flac music file, or do you have to convert it beforehand? If so, what app would you suggest to convert to mac?

As indicated by turingtest2 you would need to convert the tracks from FLAC first.

This is actually one of the few cases where the Mac is far better off than Windows. On a Mac you could use the free XLD tool - http://tmkk.undo.jp/xld/index_e.html which can convert from FLAC to various other formats including Apple Lossless. XLD can also do this and automatically add the results directly in to iTunes.

Again as indicated by turingtest2 Audacity for Windows can convert from FLAC to AAC and you can then tell iTunes to import the resulting AAC files. (They should have the .m4a file extension.) Audacity cannot directly add them to your iTunes library. Audacity can also produce Apple Lossless aka ALAC files but this is a bit more complex. See https://manual.audacityteam.org/man/tutorial_exporting_to_itunes.html

I have not used Audacity myself but in terms of file formats FLAC, AAC and Apple Lossless all support equivalent capabilities for meta tags including embedded album artwork. I do know that XLD will also convert the meta tags when converting the file format but I cannot verify myself this for Audacity.

You would need to convert. For one off projects I'd probably use Audacity but there is probably something better suited for batch conversion.

tt2