Buy credit first https://www.dc-unlocker.com/buy
1, Download Huawei HiSilicon Firmware Writer 0.0.0.24
2, Connect modem to computer, install it's original connection software if this wasn't done before
3, Launch Huawei HiSilicon Firmware writer program, modem will be detected automatically
4, Download Huawei_EC537_Firmware_11.432.11.00.45
5, On Huawei HiSilicon Firmware Writer software press white paper icon on right side of the line "Firmware File", then navigate to downloaded file, select it and click "Open"
6, After firmware file was selected, press "Update"
7, Wait for update to finish