Since LWJGL is just a thin wrapper around OpenGL, most tutorials will tend to be in C++ or another non-Java language. Also, most tutorials expect you to have at least a basic understanding of what OpenGL is and how it works.
So I'd suggest reading up on the basics, first:http://arcsynthesis.org/gltut/
LWJGL ports: https://github.com/rosickteam/OpenGL
Since OpenGL doesn't know anything about image decoders (PNG, GIF, JPG, etc) you will have to either write those yourself, or use an existing set of decoders like ImageIO (converting BufferedImage to ByteBuffer), or TWL's image decoders.
Alternatively, you could use Slick-Util, which packages some of these decoders into a small utility library. The space invaders tutorial should get you started with Slick-Util.
If all of this means nothing to you, then maybe you'd be better off starting with a higher-level library like Slick2D or LibGDX.