In that guide is very clearly specified: connect some wallet apps to your node (Zeus, Zap, Bluewallet can use the BTC wallet of your node)
You, when you save those 24 words for the first time opening your Umbrel node
If you already have another node, in its own, why would you need to sync with another node? Doesn’t make any sense.
That’s why I said that you have to change your way of thinking about what is a Bitcoin node.
Here you have some resources to study: