The BPEL QuickStart with Eclipse Designer document was written for jBPM BPEL 1.1.Beta1 and has not been updated.
You can still import jBPM BPEL 1.1.GA into Eclipse as follows. Go to File -> New -> Java Project.
Specify jbpm-bpel-1.1.GA as the project name. In fact, you can set whatever name you want.
Check Create project from existing source. Set the directory where you installed jBPM BPEL.
Set the default output folder to jbpm-bpel-1.1.GA/target/classes. Remove the examples/* source folders, otherwise many errors will appear in the problems view. The types reported as unresolvable are generated at deployment or test time.
Once the project appears in the workspace, right-click on it. Go to Build Path -> Configure Build Path
In Java Compiler, check Enable project specific settings. Then uncheck Use default compliance settings. Set Generated .class files compatibility and Source compatibility to 1.4.