Sorry, but I will not do your homework for you. It's better when you do the thinking yourself, so that you learn something.
Here are some hints:
You say you 'need to put 4 nodes in each (x,y) coordinate'. What does that mean?
You are supposed to put the coordinates into a data structure. You already called them nodes, so let's stick with that.
In addition, each node is supposed to have pointers to four other nodes. That describes a tree. There must not always be exactly four nodes attached to any other node. To be precise: This is a quadtree, used to sort two dimensional data, like your points.
So this is what you have to do:
1) Write a data structure or small class to be used for your points. They will need only two values: The X and the Y coordinate of a point. Call this structure 'node', even if it actually is not a node of the tree yet.
2) Add four pointers to nodes to the node structure (or class). Now they have all the data to act as nodes.
3) Do some reading about quadtrees. Simply start with
Wikipedia[
^].
You will have to add some methods that construct the tree.
Edit: Look at the pseudo code section in the Wikipedia article! It's almost exactly what your solution should look like. All you have to do is to 'translate' it to C/C++ and then you only have to do step 4.
4) Finish the exercise by creating one node randomly as the root of your quadtree and then creating 99 more nodes to have sorted into the tree. This is very simple, once you have understood step 3.