help with wireless- for a dunce

i’ll level with you- im a complete idiot when it comes to the network side of things. I really want to have wireless in my home. I have a laptop with a wireless g card, and a simple DSL modem with one USB going to a PC USB and a phone line going to the phone jack. Now, my sisters both have wireless cards on their laptops, so i want them to be able to get on it, so what do i need to get wireless internet around my house – in SIMPLE terms please, and is the DSL modem ive got enough. thanks.