Reference object to label a signal or variable

Good evening automaters,
I am new on Siemens DESIGO.
Sorry for theese trivials questions but despite my research, I can't find answers! Training is coming but customer is yet pushing ^^
I am on ABT site 6.0 with the hardware PXC5 on table. Inside the programming Room :
- How can we reference ("label") a signal or a variable to avoid wires into an installation canvas? Also possible between installations on the same AS to reuse an input? “Interaction to operand” doesn't find the signal on calling except error.
-Is there possibility to get an Help file to explain Function blocs and Program Blocs (I/O description and behaviour?)
By the way this suite seems nice!
Thanks for reading