For example, I will use the TP-Link TL-WR741ND v4 wireless router with firmware 3.13.2 Build 130618.
On the official website, download the archive with the newest firmware and unpack it:
You need to download the firmware for the version of which your router, otherwise it can be spoiled.
Go to the settings of the router by typing in the browser http://192.168.1.1, enter the login – admin and the password – admin.
In the menu, select “System Tools” – “Firmware Update”, press the “Browse …” button and select the firmware file unpacked from the archive. Next, click the “Update” button and wait until the firmware is loaded into the router and it reboots.
At the time of the update, you can not turn off the power of the router.
That’s all. Settings after updating the firmware reset to default.