Step 1: the language
drag Igbo over to the right
save language choices
Step 2: Make word list
Start WordList tool, choose Igbo text and make sure it is in Unicode
Here is a shot of the frequency list. 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 Igbo so it is sorted in what Microsoft considers Igbo word order.