I need parental control set up

SOURCE: internet content filtering through my router

It depends on the Router & Firmware.  BUT it definitely can be done and VERY nicely using the DD-WRT Open Source firmware on a multitude of Router brands & models.

SOURCE: I'm trying to upgrade the firmware on a belkin wireless router

upgrade of Firmware is at your risk...
never upgrade Firmwares....they are not ment for that....
your hardware may be rendered useless after firmware upgrades....the chip inside your hardware is programed to run based on a certian program installed as a firmware from the factory....sometimes upgrades will screwup your hardware....so be careful and do it at your own risk...

SOURCE: Firewall - access control settings

Short set of instructions on page 50

http://cache-www.belkin.com/support/dl/man_f5d8235-4_pm00736_0708.pdf

I'm still fooling around with it, but what I did to restrict access from my kid's machineto the internet was, browse to the router config page, default for my Belkin router is http://192.168.2.1 . Click Access Control on the menu, enable it, enter a password (this is separate from your router admin password), click the "Add" button, chose the system I wanted to restrict, specify the days and time I wanted to restrict (though I would like more flexibility here to select more than one time range), on the Service tab, verified that "Block All Services" was selected, on the URL List tab, verified that "Block all URLs" was selected, then clicked the "Apply Changes" button.

SOURCE: parental control in router wrt160n

In this particular router the is no actual parental controls but there is access restrictions that can be enabled or disabled. Disabling this should fix your concern.

SOURCE: How to set in parental controls in Beetel 450TC1 router or can certain sites be blocked through the router? Pl. help. I am a novice and have little idea.

Its Very simple ..

ACCESS MANAGEMENT >> FILTER >> Filter Type Selection >> URL >> aCTIVE - YES , Type the website you want to block e.g www.youtube.com then click SAVE ..

done