It only took me 6 years to finally get it running on both Mac OS X Sierra and Win10 wirelessly! I used to connect it with Ethernet cable to the router.
FORGET about what Brother has to offer regarding setup, they are making it unnecessary difficult.
1. First use your Ethernet connection (Printer with Router), and mark down the IP address of the printer: 192.XXX.XX.XX
2. Use any browser, type the IP in the search bar, hit return.
3. You will be at the Printer Web setup page, which will let you make changes: SSID, WAP2 password, etc.
You will need admin access to change settings: User: admin Password: access (also can be found in " Help ")
Best to download and install the BRM light admin tool to find the new IP when connect wirelessly for future changes.
The Mac will automatically find the printer and driver.
Good luck.