I can take Tiny's tutorial and redo it to be generic, but it'll take time - got a lot on my plate. Meanwhile:a
Here ya go, Old post of Icprncss at DAZ from a few years back.
Download and install the app.
Unzip the files with the rte files in them. Make sure you know what files you need to decode the files (this should be in the coded files readme) and where they are. If you don't have the key files, you can't decode the files.
Once you have all that, launch the RTE encoder app. Find the rte files. These are the coded files.
Find the output file. This is the name you want the decoded files to be. When it's showing in the output box, click ok.
You will get another screen with three lines. The output file will be listed. Locate the key file. This is the file you are using to decode the coded file. Usually it is an obj file but it can be an entire zip file. Browse to find it, place it in the key box. Usually you only need one key file. If you need more than one, the coded file's read me will tell you. If there is a key phrase, it will be in the read me. If there isn't, this screen shouldn't even come up. Same for encryption phrase. If they do and there are no phrases, I'm not sure what the heck you do. I'm still trying to find the older one that doesn't use all the folderol.
Verify your rte file, where you want the decoded file to go to and the key file you are decoding from. The phrases if they are used. If everything is there, hit ok. The files should decode.