1- Open %localappdata%/Overwolf/GameList.#######.xml" with a text editor 2- Paste the text at the end of the file, before the "</ArrayOfGameInfo>"

gistfile1.txt

<GameInfo>
  <ID>252490</ID>
  <GameTitle>PlayRust</GameTitle>
  <ProcessNames>
      <string>rust.exe</string>
  </ProcessNames>
  <LuancherNames>
      <string>Steam.exe</string>
  </LuancherNames>
  <GameRenderers>D3D9</GameRenderers>
  <InjectionDecision>Supported</InjectionDecision>
  <LauncherDirectoryRegistryKey>HKEY_LOCAL_MACHINE\SOFTWARE\Valve\Steam\InstallPath</LauncherDirectoryRegistryKey>
  <LaunchParams>-applaunch 252490</LaunchParams>
  <DetectDirKey>HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Steam App 252490\InstallLocation</DetectDirKey>
  <Input>DInput8</Input>
</GameInfo>