congratulations on installing Debian. It looks like you have a wireless device that requires some non-free firmware to run. This in itself is not a big issue, but Debian does not include this on the default installation images so you'll have to install it now. We can help. The first step is to determine what wireless device you have. To do so, open a terminal and run the following command.
This should output one line for each network device your computer has. Please post the output here on the forum so that we can determine which firmware package you need.
In preparation for the next step, can you tell us if you have a working wired network connection for the Debian machine? If yes then installing the firmware will be trivial, if not you'll probably need a usb stick or similar to transfer the file from some other machine (where you already downloaded the file).
PS. As already mentioned please forget about any exe files you have downloaded.
PPS. If you have not already found it wiki.debian.org is a great resource for people running Debian