Mo ń kọ́ Èdè Yorùbá.
* Mo: I
* ń: This is a grammatical particle indicating a continuous action (similar to "am/is/are" in English).
* kọ́: to learn
* Èdè Yorùbá: Yoruba language
Alternative ways to say it:
* Mo fẹ́ kọ́ Èdè Yorùbá: I want to learn Yoruba (emphasizing the desire to learn)
* Mo ti bẹ̀rẹ̀ sí kọ́ Èdè Yorùbá: I have started to learn Yoruba (emphasizing the beginning of learning)
You can choose the phrase that best fits the context you're using it in.