Ok, for this you will need to be able to access your router config page. To find this out go to > Start > CMD > ipconfig > The default gateway is the address you need to enter in to your web bar in your browser. From there you need to log in. Ok, now we are there this is different from router to router. However, the basics are the same.

Each PC has a "MAC Address" that is what along with an IP is used to identify the PC you are using. So, if we want to keep our network safe we need to limit who can connect to our network. Firstly, we will use Mac Filtering. What this means is that only Mac addresses you have allowed can connect to your network. This means you know who is on, and can stop potential threats joining your network.

Ok, so as I said this is different per router, but the basics are this.

1) Find MAC address by going Start>cmd>ipconfig /all this will then show you your mac address under "Physical Address"

2) Log-in in to router page

3) Browse your router for "MAC address filtering" or "Hardware Filtering"

4) Enter the Mac addresses of the devices you want to be allowed on your network.

5) Save

Now, to make sure it works well you need to have a network password. Try and use WPA2 with TKIP or WPA2 with AES. Then create a code 15 chars+ length with UPPER lower numbers.