"wireless LAN ready" is one that doesn't necessarily mean what you think it means.
To work with a wireless network a laptop must have a wireless connection card installed, and this is commonly something that slips into the PCMCIA card slot. Check your laptop specification very carefully before you assume that it doesn't need something like this.
Apart from that, all you'll need to share the connection is either a wireless access point - which is basically a base station that connects to the main PC and broadcasts to anything within range - or an ADSL router. The router is a device that connects directly to the broadband modem, and to which you can connect other computers - wirelessly, or via the conventional LAN ports that are provided for cable LAN access.
The main advantage to using a router is that the broadband connection is distributed directly from it to any other computers - there's no need to leave a 'gateway' computer running at all times.