What do I have to do to import my characters from Wiz 7 to Wiz 8?

I haven't completely finished Wiz 7, is that required or can I just put my save game somewhere?

First you need your saves from Wizardry 7; for Wizardry Gold they are .SGM files saved wherever you chose while for the DOS version it is SAVEGAME.DBS in the installation folder.

Either way, copy the Wizardry 7 saves into the Saves\Import folder in the Wizardry 8 folder, then start a new game and click the 7→8 button.

You don't have to finish Wizardry 7 but some aspects of Wizardry 8's starting state differ based on decisions made during Wizardry 7.