I need to connect my printer to my computer. It tells me it's not connected I've turned it off and on, I've reinstalled it and it says it's not connected.

You're Brother MFC printer did not come with the printer to computer USB cable. You will have to buy one;
http://www.brother-usa.com/SiteSearch.aspx?sk=5840CN
99% of printers sold do not come with the USB to PC printer data cable. Pick you're length;
https://www.cablesforless.com/c-491-high-speed-usb-printer-cables.aspx

Cheers'
Mike

Hi luna_x, the problem maybe that the computer do not recognize the Printer being install. You can do the following the ensure this is the case. Click on the Start button, in the (right) menu pane, select to open the Control Panel. Next, once the window open, scroll to find: the Hardware and Sound category, select the Printer, click to open the next window. "In the area, Name...Documents... view to see if a Printer Icon is present! If so, click to open, you may have to "Setup" the Printer to "Install" the Hardware. If not?" right above; under the File...Edit... there will be a "Add Printer" button, click on it. The Printer will become visible. If these steps should fail for some reason; do the following. (1) Turn-off the computer, turn-off the printer, unplug the printer, "you can leave the computer as is," power off. (2) Disconnect all the printer cables from the computer. (3) Next, reconnect all the cables, plug the printer in. (4) Turn on the Printer; turn on the Computer. "Do the same as above; step by step!" Note: After performing these steps "Restart the computer again to finalize the installation of the hardware. "Did this solution help? If so Helpful Ratings Feedback is appreciated, thanks paul7of9"