Confidence comes with experience.  The longer you do something consistently, the more confidence you will develop.

Understand that there is a big difference between being confident and being arrogant.  Being arrogant is a manifestation of pride while being confident is trusting the process. 

Learn all you can about leading with confidence.  Take a course.  Read books about it.  Study the life of confident leaders. 

Don't try to do it on your own. You need a group of peers who you can talk to, learn from and collaborate with.  Having colleagues that you can connect with will help you understand that you are not the only one going through this.

Ask for feedback.  Leaders who ask for feedback are seen as more confident than those who don’t.  Don't let your insecurities keep you from gaining valuable lessons about confidence.

Greet people with confidence.  Watch how you carry yourself.  Watch your posture.  Make eye contact with people.  Smile.  Use a firm handshake.

Ask for help when it is needed.  Confident leaders are not afraid to ask for help.  They glean from the talents of others.  

Stand on His Word.  Know that He is with you.  Claim the promises of His Word. 

"I can do all things through Christ who gives me strength."  Philippians 4:13

"God is our refuge and strength, an ever-present help in trouble. Therefore we will not fear, though the earth give way and the mountains fall into the heart of the sea, though its waters roar and foam and the mountains quake with their surging."  Psalm 46:1-3

"Seek the LORD and His strength;  seek His presence continually!"   I Chronicles 16:11

"Be strong and courageous; do not be frightened or dismayed, for the Lord your God is with you wherever you go."  Joshua 1:9

You and God have got this.  Be confident.  Walk outside of your comfort zone.  Stand upon the promises of God.