Access the management card by going to : https://card ip address, then go down to application notifications. You should be able make the necessary changes here.
Link: http://ftp.dell.com/Manuals/all-products/esuprt_ser_stor_net/esuprt_rack_infrastructure/dell-line-interactive-tower-ups-500t_User%27s%20Guide16_en-us.pdf
Regards,