Try to place the pieces in the box with no overlapping. There are many ways to do it.
Check here for more detailed instructions, source code, and the development stages of this applet, i.e. how this applet was built, step by step.
If you're using Netscape 4.5/Win or Explorer [4.5/Mac, 4.0/Win] then you should be able to use the slightly improved Penominoes, version j.
For your convenience, here are all the sites I can find that have OOG v1.2: