1. You need a copy of the game the same version as the translation. I'll attach my translation imported into 1.35, which is the current version on dlsite. I haven't tested it, but it should work.
2. You need to unpack Game.rgss3a. I used Translator++ to do it, which I believe uses RgssDecrypter, but there are probably other tools you can use. That will give you a Data folder and a Graphics folder. If the unpacking utility didn't remove Game.rgss3a, rename it or move it, otherwise the game will use that instead of the folders.
3. Copy the rvdata2 files from the translation into the Data folder, overwriting the existing ones.
The game should be in English after that, minus the menus which I can't translate without breaking the scripts file.