Well I assume you arent given a "Vertex" class or anything, so thats where you would start I imagine. A simple "struct Vertex" is probably good enough--it needs two fields, the vertex it is connected with, and the cost of that edge. So something like this should be ok (the syntax might be incorrect, because I dont remember the syntax--but thats a minor detail)
Overall, the struct might be a "vector" of "linked lists" of "Vertex"s. Each element in the root container "vector" contains a list of vertices, which is your adjacency list.
Say we had a small direct weighted graph and it is represented as a triple (v1, v2, w) where v1 is a vertex that goes to v2 with cost w. Say we have: (1, 2, 0), (1, 3, 5), (2, 3, 1), (3, 1, 0). This could be represented as a vector with 3 linked lists, such as:
1 -> (2, 0), (3, 5)
2 -> (3, 1)
3 -> (1, 0)
Where, for example edge 1 goes to edge 2 with weight 0, and also to edge 3 with weight 5, etc.
Well to create the graph you need to know the vertices and which one goes to which. Therefore you need more than just a "costtype none" argument. You would need something like an array/list/vector/any collection of "Vector"s. So you take in the list of pairs of vertices and assign them all weight 0.
there is a function called weightedGraph(Costtype none) that is supposed to create a directed graph giving all edges a weight of none.
If you are overwhelmed with some task, such as this, do not look at the big picture (in my opinion): start with the very basics, which is the required data structure which is what I described above. After you have that then try and create one given, say, a 2-d array of integers, i.e.
Of course, again the syntax might not be exact because I dont remember it and am just typing it without testing. So the function takes in a 2-d array of integers with length "len", so using the example vertices I said above, it might be called like:
vector<list<Vertex>> createGraph(int ** vertices, int len)
So this function should create a vector linkedlists of "Vertex" structs, and assign each "weight" field 0. For example, at index 1 of the vector you create the linked list with "Vector" structs (2, 0), (3,0).
// pair (1,2)
vertices  = 1;
vertices = 2;
// pair (1,3)
vertices = 1;
vertices = 3;
// pair (2,3)
vector<list<Vertex>> = createGraph( vertices, 4 );
Anyways, I think Ive given more than enough to get you started.