from the top..
you've got to the right page in your router.
open up a command window/ dos prompt.
type in "ipconfig/all" without the quotes
you should see a list of settings and if you have more than one adapter installed you need to choose the right one.
you will see an item "physical address" with a series of letters/numbers after it, should be 6 pairs.
write these down
"exit" dos window
go back to your router setup page where you've seen the mac filtering options.
click to enable mac filtering.
where you have the space for 30 odd items just click in the first one and enter the 6 pairs of numbers/letters;
the first line will be for your main pc
the next line for the next pc,
click "apply" if that is an option
Don't worry about all the other rules just yet
if you look at your info page for the router it will eventually show which pc's are connected to the router. i.e. there ip address and their mac address.
that should be enough to get you going
p.s. mine is a different router but same rules should apply.
wait with baited breath