Since nothing is mentioned about the start vertex in the question, let us assume it as vertex 1 i.e. s=1 in step 3 of algorithm.
To start with, start vertex (1) will already be in mst, i.e. v(1) = 1.
Loop in step 5 will ...
Apart from showing stepwise addition of vertices and edges to a MST for the graph, solution also explains the Prim's algorithm briefly.