#1 Download the Savegame.
#2 Rename the file! Use your SteamID ( steamid.co and use your STEAM64 ID )!
#3 Place the .save file there: C:\Users\<<<Username>>>\Documents\My Games\Rocket League\TAGame\SaveData\DBE_Production\
#4 Delete / Backup all other .save files and just leave the new file there
#5 Profit!