Hi Carlos,
You don't need any document.
In 3.x we use generate export data source to load data from one target to another target.
its data mart concept. But bw 7.x there is no data mart concept.
So now you want load data from Cube1 to Cube2.
This will your data flow Data source---->cube1--->cube2.
Go to your cube2-->rigth click-->create transformations, use source cube as Cube1.
Do the mappings as you need.
Later create dtp at cube2.
Thanks