You can follow the mod guide if you have not done so already it will cover everything except for thumbnails.
It seems that your pathing is correct, at least for the output file. Files within the mods folder should be visible on the modding hub so I'm not sure what's going on. When you build the mod is there no errors or warnings?
Possible solutions, from easiest to hardest, would be:
1. Verify integrity of game files.
2. Make a backup and change the name to something other than ACX.
3. Make a new, blank tuning pack and see if that shows up on the modding hub.
There's a few other things we could try but see if these work for you can we can proceed from there.
As mentioned in the first paragraph to get a thumbnail (preview image) you will have to change the game version to 32 bit and upload the mod. You can change it back to the normal version and it will keep the thumbnail.
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#Steam AliasWL%Streak
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