Hi, I'm Bhavik. Welcome to JustAnswer. I'm reviewing your question now, and will reply back ASAP.
Do you get any error like communication error while you use it without USB ?
Do you see the green WiFi light on the front of it ?
You are having Epson Stylus NX420 All-in-One Printer right ?
What is the name of your wireless router or wifi name ?
Cool, I Just wanted to make sure that you have wifi with you . You need to use the CD which came with your printer . Do you have it with you ? if So, Insert it in your PC.
Try these steps directly setup from printer :-
Did this help you ? Are you satisfied with my answer ?