Prepare a creation that shows off the best that you are capable of doing in that area right now. This might be, for example, a song you have written, a piece that you have been practicing on your instrument, or a short essay describing what you hear when you listen to the music that interests you. You may have to prepare this creation "from scratch" or you may be able to polish up something you have already worked on. If you have no idea what kind of creation would show off what you know right now, consider doing the inquiry in Creative Responses to Music Learning.
As you prepare your creation, make a list of any problems that you cannot seem to solve, any weaknesses that you do not know how to fix, or any specific learning goals that you think might make it better.
If it truly is not possible to prepare a creation to show off your present abilities, then prepare a set of well-thought-out, thoroughly researched, intelligent questions instead. (For example, if you have not even bought an instrument yet, you may want to research instruments and then ask some well-informed questions about what you should buy.)