1. I chose my Igbo text in the text file chooser.
2. Then I tested whether it was already in Unicode by pressing the 
button . The answer came that it was in UTF8 (a combination of one-byte
and two-byte systems, not compatible with WordSmith) and an offer to convert
it.
3. I converted it to 16-bit Unicode (what MS Word calls "Unicode" if you save as .txt).
Then I made sure the language had Unicode checked.
4. Then I made my word list in the usual way (WordList | New ...).
Here is a shot of the frequency list. I increase font size to 12 so you can see the dots under O and I and U.
I don't know Igbo and therefore cannot be sure the word order is correct. At the moment WordSmith "thinks" this is English so it is sorted in English word order,
but still, the O with a dot beneath is together with the O without a dot.