I don't think I struggled as much to get it working. I followed the Wiki for how to get it installed and working with the Lazarus IDE. If you install the package into Lazarus for Pas2JS integration as the Wiki mentions, it makes compiling programs with it easy. The Lazarus package adds a few extras to the IDE which are needed to get the compiler to work correctly with it. There was another problem I ran into, as I am using the current stable FPC that doesn't support some newer modern Pascal syntax Pas2JS uses, I had to add a new IDE Macro called InLazIDE and put ifndef around a lot to get code completion to work correctly. But once I got that worked out, it was smooth sailing afterwards.
Also, don't expect to design your app using the Lazarus RAD designer and then magically make it all work on the Web. That's not what Pas2JS can do just yet. There are some widgetsets available, but I haven't really dived into those just yet. But as an awesome way to write Pascal that can be compiled to JavaScript, it's great once you understand some of the differences between using it and regular FPC/Lazarus. The Types and having to Typecast a lot really got me at first, as I don't tend to use typecasts very often in regular FPC/Lazarus, but it's almost a requirement for Pas2JS.