In these verses, Jesus tells us to seek His kingdom first and all the things we need while we are on the earth will be supplied for us. Then He tells us not to be alarmed and struck with fear because the Father joyously gives us the kingdom realm with all its promises!(AMPC)
A kingdom is a realm in which a king sovereignly rules. Our king is Jesus. God has given him all authority over the earth. It was given to Adam, but he lost it. Then Jesus bought it back with His blood. Now every "thing" has been placed under His rule. Eph. 1:21 says He is far above any ruler and authority, power and dominion, and every name that is named, not only in the present age but also in the one to come. Your "thing" has a name. Your "thing" has been placed under the rulership of Jesus's kingdom.
A king rules by decrees and you can find them in the Bible. A decree is a formal and authoritative order having the force of law behind it. We seek first the kingdom by searching out the decrees he has made concerning our "thing". Then we are to declare that truth over our "thing" with the authority Jesus has given to us. Job 22:28 says "You will also declare a thing, and it will be established for you; so light will shine on your ways."
Jesus is not asking us to do the impossible here. There have been many situations in my life when I found myself alarmed and fearful about "these things". In those times it is especially important to remember to seek first His kingdom. Go before the throne of grace and ask for the help you need. Search out His decree and declare it knowing that the Father is delighted to take care of your "things".
I like the way the Message Bible says this:
“What I’m trying to do here is get you to relax, not be so preoccupied with getting so you can respond to God’s giving. People who don’t know God and the way he works fuss over these things, but you know both God and how he works. Steep yourself in God-reality, God-initiative, God-provisions. You’ll find all your everyday human concerns will be met. Don’t be afraid of missing out. You’re my dearest friends! The Father wants to give you the very kingdom itself.
Luke 12:29-32 MSG
---Is there an area of your life today that is causing you to be alarmed or fearful? They are part of God's promise that all these things shall be supplied to you. Write the "things" on a 3 x 5 card. Find a kingdom realm promise in the Bible and write it down. Every time that fearful thought comes, declare what the king has said about it. See the "thing" as God sees it, under the kingdom rule of Jesus.