My Wi-Fi router password has remained constant since its installation several years ago. Now I was informed that some people are tapping on it without permission, thereby consuming the data quota per month, significantly slowing the speed. So I had to Google this, and of course, several hits are returned. Nothing was helpful because of variation in the terms used (e.g., the term password is not mentioned). I called customer service (211) and all is now clear.
The first step is go to 192.168.254.254 (I'm using Chromium so the layout may be different). Then click setup at the bottom right of the page. In the authentication query, input user in the user name text box, and user in the password text box, and click the Log in button. Click setup at the upper left portion of the page, then click WLAN at the left column. Click Security option below it, entering the Wireless Security Setup. Look for the Pre-Shared Key password box, and type the new password there. Then click Apply Changes. Then click Logout. That's it!
Happy fast and secure computing!