In a terminal type:
deb http://security.debian.org/debian-security jessie/updates main non-free
This will add the repository with the drivers for you and make it effortless to manage dependencies. Of course the next step is to install it. Type:
sudo apt install iwlwifi
Once you have done that you want to avoid the rest of the proprietary packages, In order to do so you need to go into your repositories list. Idk where this is located because I use a different free software distro called parabola. However the best guess I have is in /etc/apt/sources.list. So go into a terminal type:
sudo nano /etc/apt/sources.list
Use that command to remove the repository we added earlier.
Your homework is to use the man (manual) command and learn about the command deb & nano.
The way to become a user who can self solve problems is to type out the commands listed and not to copy paste them, although pasting links is fine. Hope this helps let me know if this worked.