How can structuralist theory be applied to an African text?
Your question is really interesting. I'm not certain that I fully understand it, but I'll do my best to answer, using a Q&A format of my own.
Q. Can you apply structuralist theory to an African text?
A: In our age of multiculturalism, many people tend to be skeptical about applying a Western theory to a non-Western text. They would answer the above question with a clear "no." The structuralists of the late 1950s and 1960s, however, would generally have answered "yes." They tended to believe that all languages (and all cultural productions, including literature, whether Western or not) are governed by the same hidden, universal rules. To them, something being Western or non-Western didn't matter all that much in the end.
Q: Can you give an example of how to apply a structuralist theory to an African text?
You may be interested in applying a structuralist theory to an African folktale and to a Western folktale and then comparing the results. One of the most diirect (and earliest) theories that you might consider applying is the list of 31 functions presented by Vladimir Propp in Morphology of the Folk Tale. Propp's list is very clear, as is his argument. He claims that folktales around the world follow very similar patterns, and he seeks to lay out those patterns in very clear and direct terms. You may find yourself agreeing with or challenging his view that all folktales (whether Western or not) can be approached and understood in the same way.