How do I ask for advice from someone I've never talked to before?

This girl goes to my gym and we dont really talk much just the occasinal smile but me and my other friend were talking and i said i needed advice and they told me to talk to her but the subject is pretty personal how do u think i should start the conversation?How do I ask for advice from someone I've never talked to before?
That's basically what you're doing now... Asking advice from people online you've never talked to before about asking advice from someone offline you've never talked to before..