As mentioned above, Delaunay triangulation is a rather complicated algorithm for this task. If you accept O(n^2) running time, you may try Ear Clipping algorithm which is much more easier to understand and to code. The basic idea is the following. Every polygon with >= 4 vertexes and no holes (i.e. its border is a single polyline without self-intersections and self-tangencies) has at least one "ear". An ear is a three consecutive vertexes such that the triangle built on them lies inside the polygon and contains no other points of the polygon inside. If you "cut an ear" (add a triangle to the answer and replace remove the middle point of these three points), you reduce the task to a polygon with less vertexes, and so on. Ears may be trivially (by definition) found in O(n^2) resulting in a O(n^3) triangulation algorithm. There is O(n) ear finding algorithm, and, though it is not very complicated, it is rather long to be described in a couple of phrases.
Furthermore, if you need faster algorithms, you should look something about monotone polygons triangulation and splitting a polygon into monotone ones. There even exists a linear-time triangulation algorithm, but its just as complicated as Delaunay triangulation is.
You may consider Wikipedia article and see an small overview of existing methods there.