minimal spanning tree in c++

"An object of type Graph represents a weighted graph. It has four fields:

the number of vertices in the graph, the number of edges in the graph, an array of Edge structures that holds the edges, the physical size of that array of edges. Include a constructor Graph(nv) that yields a graph with nv vertices and no edges. The constructor must create the array of edges.

You can assume that there are no more than 100 edges, but that number must be easy to change. To increase the maximum number of edges to 200, for example, should only require changing only one line of your program. To achieve that, create a named constant that is the maximum number of edges. For example,

const int maxEdges = 100; defines constant maxEdges with a value of 100. Any time you need to refer to the maximum number of edges, use maxEdges, not 100. All structure types must be documented by saying (1) what an object of this structure type represents and (2) what property each field represents."

I have to write a program that will create a minimal spanning tree in c++. I am an extreme beginner at programming and am having trouble with how I should write this structure.

Any advice would be greatly appreciated.