Configure Belkin Router to Connect 3 PC Via WiFi

Our house is WiFi zone but I am the only one using it, but now that my sister have her own pc i wanted to share my speed access to her. I wish to cap the speeds of my sister's net access something like or near to 100 kb/s, so that will be for (PC and PS3) for her and for may papa.
My sister's pc and I have PCE-N13 300 Mbps adapters while on the other hand my papa has some tp-link that also or which have the same thing as 300 Mbps. And the wireless router is from Belkin, so how can I make it? Any idea?
