Therefore let us (with privilege) approach the throne of grace (that is, the throne of God's gracious favor) with confidence and without fear, so that we may receive mercy (for our failures) and find (His amazing ) grace to help in time of need ( an appropriate blessing, coming just at the right moment. Hebrews 4:16 AMP
When we say that someone is bold, we are referring to the fact that they are confident and courageous. We can't go boldly to the throne if we don't know the king. This requires having a relationship with the person that you are engaging in a conversation. Additionally, I can also approach the throne with boldness by reminding the king about what he has already promised me.