The MLA Handbook does not provide explicit direction on citing Indigenous Knowledge and Indigenous Elders.
Norquest College Library has provided some guidance on this in the spirit of reconciliation. You can see their example for a works cited listed entry here.
Unlike with other forms of personal communication, Indigenous Knowledge and Indigenous Elders should also have an in-text citation. To include an in-text citation include the speakers name either in the narrative of your sentence or at the end within parentheses.