Unfortunately it is not yet possible to modify or add a financial year. We are developing this functionality and hope to have it soon. On the reports you can still choose the time: go to the Reports tab -> choose a report -> see Period -> choose months / dates -> Set period.
This means also that it is not possible to create documents outside the current financial year (1.1.2017-31.12.2017).
We apologize for any inconvenience.