How to use union-find, minheap, Kruskal's, and a sort algorithm to create a minimum cost spanning tree? (C++)

Question

I apologize if this question is a bit broad, but I'm having a difficult time trying to understand how I would create a minimum cost spanning tree. This is in C++ if it matters at all.

From what I understand, you would use Kruskal's to select the minimum cost edges for building the spanning tree. My thinking is to read the edges into a minheap and that way you can remove from the top in order to get the edge with the minimum cost.

So far I've only been able to implement the minheap and sets for union-find, I am still unsure of the purpose of union-find and a sorting algorithm for the purpose of creating a spanning tree.

I would greatly appreciate any advice.

EDIT: I am not limited to union find, minheap, kruskals, and a sorting algorith, nor am I required to do any. These were just the items suggested by the instructor.