Transfer your mesh from GMSH to Matlab

I believe examples are on of the best ways to learn, so I start from an example.

1- build your geometry in GMSH (you can easily do that by studying the first tutorial of the software)

2- Mesh the geometry by going to the Mesh tab and clicking on the 2D. This will build a triangular non structured mesh

GMSH

Here is the link to a very useful free mesh generator and post processor software (GMSH) which is distributed under the terms of the GNU General Public License (GPL). http://geuz.org/gmsh/ There are versions available for Win, Mac and Linux.
You can find tutorials in the tutorial folder of the downloaded file.

Below is an example of unstructured mesh for a circular surface with a squared hole inside.