Are you’re using the Home Edition or the Standard / Professional Edition? If the former, then see Adding OpenType Features tutorial. If the latter, then use FontCreator’s built-in OpenType Layout Features editor.
If your font is designed so that these ligatures should be used by default, use the rlig (required ligature) feature. If you want the user to decide whether to use them, then use the liga (StandardLigatures) or dlig (DiscretionaryLigatures) features instead.
The ligatures must be defined as new glyphs, so add three more glyphs, import the outlines from Illustrator, resize them to the right height, then use the Glyph Properties toolbar (F3) to rename the ligature glyphs to ir, jr, ra, etc., and click Apply. They don’t need to be mapped since they will only be used by applications that support OpenType features.
Open the OpenType Layout Features editor from the Font menu:
Caut and paste the code below to add the appropriate glyph substitutions:
script latn {
feature RequiredLigatures;
}
feature RequiredLigatures rlig {
lookup RequiredLigatures;
}
lookup RequiredLigatures {
sub i r -> ir;
sub j r -> jr;
sub r a -> ra;
}
Click the Validate button to see if it works. If it does, close the editor to save the changes to your project, and test the features in the Font Test window (F5) by typing ir, jr, ra, etc.