Translation:I have to think about what I am going to wear.
There are lots of different words for "wear."
Tricky. Reverso translates it thusly: I must think what I go away to putting; Google: I think what I'm going to put. Ponerse, the reflexive version of poner, means to put on (clothing) Unfortunately I kept trying to use the irse version of ir...to go away, so just couldn't get the right answer....But I am not sure about the pensar qué. I'm guessing the qué is the "that" so debo pensar: I have to think about...the qué is the "that" and the me voy a poner is "I am going to put on (or wear)" Of course, I forgot all about ponerse, and as I wrote earlier, kept trying to make sense out of me voy a as I am going away to......