The installation program needs to get information from your printer in order to successfully complete.
Please make sure that the printer is connected to your PC and switched on before clicking Next to complete the installation, otherwise you may need to repeat the install process.
If you are unsure which port to use, connect it to the top-most or left-most one. Most cables only go in one way round, so if it doesn't seem to fit, try it the other way round. If you are using USB, then it doesn't matter which port you use.