The process is easy.
Find a replacement of your choice on the DLS, built in, or some other website.
Copy the KUID by either writing it down, or view asset in separate window and copy the KUID from the bar at the top.
Open the config.txt file for editing.
In Notepad or some other text-only editor such as Notepad ++, look for the missing kuid.
Replace that with the one you copied or are going to type in carefully.
Repeat the replacement in the kuid-table.
Save and close the config.txt file and submit the asset.