To watch this process via video, Please go through the video:
The first step is to take Backup of your Data. For backup go to System -> Data Backup- Daily Backup
A Window will open you can select a path of your backup file in that. In case if you want to save your current year financial year data backup in another path besides the default path you can change the path and change the name of the file with the current year mentioned in the name and save it.
After this process go to System -> System Maintenance- Close Financial Year
A window will open and you have to select "Select all" and "Change financial year for all users" and press ok button.
A success message will appear. Select ok to the option
Now you have to close the software and login again. Your financial year has successfully changed and you can now start your billing in the software.