How to save new additional character in Soul Calibur?

Well, its easy, you gain the character, and soul calibur will auto save it. After you gain it, and you see the soul calibur main screen, exit the emulator, and start the game again, you will have it.

Question= on the verus screens (i.e Mitsurugi vs Sophitia, Voldo vs. Taki, etc....) do you get some graphical errors in chankast?

Did you correctly format the vms.bin? If not boot up chankast with no disc/image and then proceed to the memory card manager and format the vms.bin, also make sure the file is not read only

As said above, soul calibur autosaves the characters etc.. as you gain them

Yeah, that happens to me too, thats why after getting the new char, before you start the second game, you must EXIT chankast, and restart it again. If you get an error window, chankast doesnt save anything (not even the cd rom drive you selected to boot your games from).