What would you consider the things above?
Read the rest of the chapter. Paul provides enough detail to know precisely what he's talking about, don't you agree? Don't you agree that he explained his mystical language in verses 1-3 quite well in the balance of Colossians chapter three?
It's about ethics, or morals, largely, we would say. There's doctrine yes, but it's 'heavy' on ethics too. It's what we believe, but it's also what we do. And it's not like what we do hinges upon what we believe either, if you notice. He 'spells out' all the topics he's trying to talk about, he's got a pretty extensive list of things both to pursue and do, and to avoid.
It's completely fascinating that the things above are ethical. Paul says we're already in heaven right now, in Christ, and his Apostolic council is to dwell and meditate on ethical matters. It would seem that already being in heaven, why bother at all with ethics? Let's just indulge and succumb to our original sin's suggestions, since that's the 'easy' thing to do. Or so the thinking might go.
But the balance of Colossians chapter three crushes that notion as its polar opposite, on the contrary, you very much should dwell on matters of ethics, sometimes also called morals.
(The 'morals' versus 'ethics' confusion is aggravating tbh, it's complicated but it's not that complicated, let's not make it more complicated than it is, but it's like pinning down a fresh watermelon seed the way it's talked about now, and I mean everywhere. Because there's no 'dictionary' for the words, and how they relate, that's authoritative. Everyone means something else whenever they use these words 'morality' and 'ethics'.)
I would consider that to be keeping our focus on Jesus, who He is and what He has accomplished. Of letting the Spirit sanctify us through His word. Of growing in our knowledge of God. All these things are found in His word, and growing in them is without limit as we learn to trust in who God is. And all these things are held as truth in the doctrines of Christianity. The doctrines of God, of Christ, of Salvation, that come from the Bible. Those things that Jesus and the Apostles taught. Man's condition and need. God's glory.
I find that these things are often skimmed over at best and the focus is on the things of the earth. God and Christ become almost in our peripheral vision as a benefactor. And instead of preaching or defending the gospel we argue over things like the millennial reign and the rapture and two gospels or one. We frankly seem to have a religion that is self centered and not God centered. And we are ill prepared in my opinion to even defend the gospel from a deep and abiding conviction and knowledge. Ill prepared to even notice the wolves in sheeps clothing or even care, let alone have the first clue how to defend ourselves or our flocks.
Paul is trying to advise the Church how to 'remind' themselves that they are already seated at the right hand of the Father in Christ in heaven. This is how we do it, we focus on ethics, on our ethics, and our ethics isn't ambiguous since it was preserved by all the Church's bishops since the time of the Apostles. Of all the doctrinal disputes there's no moral disputes, so we can be confident that this witness has been very well preserved.