How to make OKI ML 491 work

I've purchased a used OKI ML 491 printer on e-bay. But it's not printing.  When I opened the printer's tool box, it appear error message. 

I've spent more than 12 hours and finally, I found the way to make the printer work. Here is how I make it work, just in case someone purchased the same model printer and got the same problem.

1. Go to OKI website to download the driver and user guide.
2. Install the driver.
3. There would be a couple tool boxes shortcut appear on destop, if you open them, you may see some error message such as Wrong Printer, or Not Working. Just ignore them. 
4. Follow the user guide to set up something by press a few keys on the printer.
5. On the computer, after choose this printer and press "Print", PRESS the SEL key（The first key on left of the printer). Then the printer would start to print.