Your printer does not have a password, but your router does. If you have installed any third party application that secures your apps, enter the password that you have assigned for unlocking the application and try.
Check whether the latest printer application is installed on your phone before you start. If your printer has a display panel, select Settings -> Network Connection or Network Settings.
Choose Wireless Setup Wizard or Network Setup for further assistance and the printer looks for a list of nearby networks, choose your network, enter the credentials of the router and tap Connect.
Go to your phone settings and check whether the printer is added to the list of devices in the Devices menu. If you are an iPhone user, open AirPrint and check if the latest version of it is installed.
Open a document or photo and select the Share icon.
Now select the printer from the list, and tap Print.
Make sure to complete the printer setup process properly and start printing.
Guess what! You need not use a router to print wirelessly if your printer supports Wireless Direct.
Just keep your printer and computer close to each other while printing using Wireless Direct.
Printer setup Blog 