CryptImportKey

[DllImport("Advapi32.dll", SetLastError = true)][return: MarshalAs(UnmanagedType.Bool)]
public static extern bool CryptImportKey(
   IntPtr hProv,
   byte[] pbData,
   uint dwDataLen,
   IntPtr hPubKey,
   uint dwFlags,
   out IntPtr phKey
);

Microsoft documentation: Link