What is the French translation for stand in your own truth?

This is an idiomatic phrase and, as far as I am aware, there is no French official translation of Oprah's phrase. Assuming the phrase means something along the lines of "realize who it is that you are and embrace that", the French translation of this meaning would be, "Rends-toi compte de qui tu es et épouse ça."

You could also say, perhaps more idiomatically, "Bagne-toi dans ta réalité" which means "bathe in your reality".