Open it and read the provided instructions. But essentially you will copy it onto your 0.13 directory and choose "replace all" when prompted.
You can move that in, too. That folder is specifically designed for patches- if a saved game can't find the right place in a script, it starts rolling back to somewhere it can correlate the save with the script. the Old Game folder is a previous version of the compiled scripts to work as an in-between bridge between a save and the current script, increasing the chance of success. If it still can't correlate, then you get the normal error about "couldn't find a place to stop rolling back."