All I can offer is hints or tips, as actual passwords will be set somewhere else.
Unless you're using your Macbook as Host, you need to know the password of your Wifi network.
Many Routers will come with password automatically set, which is often written on the device or on a card attached to the device. However wifi passwords can be changed by the user with admin access, this will disable most Wifi devices when the password changes.
If you can connect to the wifi already (or connect with cable) with another device, you may be able to log in to the Router settings. You'll need to find the address by seraching the Devices Support pages/docments. This will often have it's own pass word as well, however this info may be on the support pages to help out.