I have found the easiest way to connect with parts that I don't know is just to be patient work on meditation mindfulness just talking to them and telling them that you accept them you love them you're not going to hurt them they're trying to protect you they need to understand that you don't want to make them go away but you're anxious or curious to get to know them. When they feel comfortable and safe they will finally introduce themselves to you.

You need to understand that even the most unwelcome parts in our mind in some way are there to help you. They don't always go about it in the correct way but it there perspective they are being helpful. Vice versa they do not understand that you mean no harm. So it just takes time patience and gentleness on your part you can't push it.