Your xye game folder has a sub-folder called levels, you can place the level file in this folder. Then restart Xye and you will find the new level in the list
The usual installation creates a (hidden) folder called .xye in your user home folder. Get a file browser and go to /home/yourusername/.xye/ find the levels subfolder and copy the new level folder to that location.
If you have any level that you made in the editor and would like to share, feel free to email it to vexorian@gmail.com and it might be featured in the blog.