In order to have the ligatures working you need:
1. A font with properly defined ligatures. The glyphs must be somewhere, those with Unicode slots, can be placed there, other ligatures should be in a private area. Then there must be some setting that tells when to use the ligature, I don't know about FontCreator, but for FontForge see
here.
2. A program that can actually use the ligatures defined in the fonts. I seems the ADE 1.8 preview can, and previous versions cannot. If you want to test the font, look for a program (web browser, text editor...) that uses ligatures in other fonts, and then try your font there.