network credentials

If this local wireless network is in your home, then you must have set it up when your modem/wireless router were installed/set up. At that point, a network name and password had to have been set up. Sometimes, your ISP will provide a default network name and password (mine did), but it can be changed. In any case, there is a sticker on my modem/router combo which has that info on it (if you did not change it). In order to your wireless devices to be able to connect to the router, you need to enter that info and "register" the device with the router. If you can't find it, call your ISP and/or go to the modem website (something like 168.192.x.x - should be in your setup info guide) and you can change the info there.

You should be able to go into System Preferences > Network on your laptop and delete that network, then try to join it again. However, that just joins the same network for which you will need the password. The password goes with the router and it set there, so you can't change it anywhere else - you need to change it there; either on their setup website or by calling your ISP (most likely will need to call because your router is preconfigured with that).

It wants the user name and password for a valid account on the laptop. If you can't remember the password, go re-set it on the Windows laptop.