This is not generally a one or two step process, and the procedure is not the same for all printers. And in any case, no one here can help without information about the printer brand and model, and the version of Mac OS X on your computer.
Suggest you get in touch with the printer manufacturer and see if they can help. I know that Brother does provide phone support. Don't know about other printer brands.
This should be pretty easy, Apple provides some basic instructions but because there are hundreds of printers what is needed for your specific printer you may need to look at instructions that came with your printer.
Please first read Apple's OS X: Connecting a Wi-Fi printer to your Wi-Fi network located at http://support.apple.com/kb/HT3500