To set the white balance, put something white where your subject will be. Zoom or get close enough to fill the frame with white. Take a shot. Then go into the menus and go to where you can set a custom WB. It will let you choose an image so pick the white shot you just made. I think you also have to set the WB on the top panel to to custom.
Learn to use RAW, there is a current thread about shooting RAW.
With RAW, the white balance setting is not actually attached to the image yet...only when you open and convert the file, is the WB applied to the image. Therefore, you would be able to adjust the WB of the shots after the shoot, during the post processing stage. You can even make one adjustment and then apply those settings to the rest of the shots...since they have all been shot under the same lights.