This simulation is created with EJS and the file you have download is in jar format. (Alll the simulations I have created since 2001 were using EJS).

You can double click the file to run it if your computer support java.
Right Clcik inside the simulation, and move down to [u][b]GUI options[/b][/u] , you will find [u][b]translate[/b][/u] sub item.
Select the [u]translate[/u]: move mouse to that item and release mouse.

A new window will popup with many strings in two columns:
1.You might need to select the language you want to translate to.
2. change the strings in the second columns
3. Click Save and it is done. (If you want to see the change , [b]RIght click[/b] again: [b][u]GUI options[/u][/b]->[b][u]language[/u][/b]-> "the language you translated to".

There are many other options: data tools....

You can change the image files,too. But, you need to replace/add new file into the jar file to make it work.
The jar file is the same format as ZIP. You can unzip it and add new image file. Pack file back to ZIP with the same structure, then, rename ext to jar. And double click again to run it.