Log into the web portal on a local server, select IP Office Web Manager
Sign in using the credentials found on the CP username list
Go to call management>extensions
Then find the extension you need to update/change in the search bar, and select edit
Update the password here, and select Update at the bottom
Then, go to call management>Users
Search for the same extension, and select edit
Now set this to the same password you set the extension at, and select update at the bottom again.
After this the user of that extension should be able to log into their phone with that password.