Untar or unzip the file you just downloaded. You'll want to read the file docs/readme.txt.
To run TAXI, go to the taxi directory (for example, taxi-1.2.1), and run java -jar lib/taxi.jar
The first time you run TAXI, open the Help dialog (menu Help/Help, or press F1), and read the topic Getting started to set 2 important things. If you don't do that, the first transformation will fail. You just have to do it once. When it is done, close TAXI so that your configuration si saved, and re-open it.
It is highly recommended to let a console open to be able to see, if it occurs, the following error (Bug 3) :
java.lang.OutOfMemoryError <<no stack trace available>>
This might happen when the editor is rendering the graphic. If you find that the editor takes too much time to render the graphic, check out the console to see whether the previous error has occured. I haven't been abled yet to intercept this error (it is raised somewhere in Batik code). If it happens, this is because the Java Virtual Machine can't get enough memory. Better close the editor, and restart it with an extra option, like this : java -Xmx256000000 -jar ./lib/taxi.jar. With this option, you tell that the maximum heap size is set to 256Mb. You can specify any other value.
Note: Java must be installed : JRE 1.3 or above. It is recommended a 800Mhz processor and at least 256Mb RAM.