Don't confuse your ADSL modem with networking. They are two independent systems, although, interrelated.
Your ADSL modem is connected via the USB port in the normal manner.
For a simple system, all you need is a suitable wireless card in each machine, but make sure they are compatible with each other. If possible, use the same manufacturer. click here
You can use this link to find alternative methods of connection too.
Set up the network first, so that each machine can see the other. Then if required, set up internet connection sharing (ICS), to enable you to use the internet on each machine. For this method, you will need the computer connected to the modem to be on, whenever you wish to access the internet via your laptop.