The password should be the same one as your home one.
Just go to setting on iPhone then wifi then it will bring up your network and then ask you for a key put the same key that you use for your home network. If you don't know it you will need to login to your wireless router and get the key from there or make a new key up but if you make a new one you will have to change that on all computers connected to the network. I hope this helps you.
If i have misunderstood your question please tell me because i have setup hundreds of wireless networks.
If you're trying to get on the laptop, you need to setup peer to peer networking. However, if the laptop is connected to a router in an Ad Hock configuration, then you will not be able to connect correctly.
If you are trying to get on the router that you also connect to with the laptop, then you need whatever security key that was set on the router.
If you don't know what that is... Well, you would have to completely reset the router and start from scratch and setup a new security key.
If the Wireless network that you are connecting to for the laptop is not your own and you are leaching the signal from a neighbor, then I don't know what to tell you. Technically, if the laptop can connect without a password, then so should the iPhone. And if the laptop is connected with a password, but you don't know what it is (how is the world could that happen?) then I would have to say that you are SOL.