Comparison with same period last year

[Newbie777]

Hello,

I'd like to combine the sum function below with 

Sum([FBL3N by employee.Amount in local currency])

another date and time function below:

AddMonths(today(),-12)

I am not sure how I can combine these two expressions, as I am not familiar with Qlik Sense syntax.  I'd greatly appreciate it if anyone can show me how to do it.  

Thank you very much for your help.