If you are lacking in the Linksys RE6400 Setup then, you need to read the short guide. Additionally, do not forget to place the devices at a near distance and keep the devices properly on from the power outlet. After that, connect an ethernet cable to the devices. Then check straightforwardly for firmware updates on your device. As it is a mandatory option to make your device software bug-free. You will see a simultaneous speed enhancement in the wifi device after firmware updation of the device.  Although many devices update the firmware itself. Although many of them need to be updated. You can check for it through the device app or the interface of the browser. Lastly, create your own password. Most of the router comes along with pre-designed password and usernames. In some, you need to create a new one.  So create one for your device account, or just check the manual of your device.