Take a look at the On line Tutorial and these fonts made with Font Creator by Pia Frauss.
I find it quickest to paste bitmaps copied to the clipboard directly into the Font Overview window, though the import image method offers greater control.
One thing you need to take care about is scaling. If you need to scale the characters within font Creator to make them the right size, make sure that you scale them all by the same amount. Use the Glyph Transform feature on all of the imported characters (after saving) to scale them all by the same amount.