So there has always been documentation available for using jACT-R within Eclipse, but I don't think anyone knew about it. So, I've made a few things more obvious. New users will now be greeted with the Welcome screen that includes jACT-R specific hints. Already running? You can see this content via Help - Welcome.
This includes automatic links to the included documentation (opened in your preferred web browser) and two cheatsheets. One cheatsheet is an intro to using Eclipse from the jACT-R perspective. The second is the unit one tutorial.
As more questions arise I'll expand the documentation and cheatsheets.
Enjoy.