Standard benchmarks such as the S&P500 and Russell indexes are commonly used for performance analysis because of their ubiquity. However, they represent specific asset classes so they are not appropriate as a benchmark for a diversified portfolio that covers multiple asset classes.
With Portfolio Lab, you can build a model portfolio made of indexes, and use this model portfolio as a benchmark. To create your benchmark:

1. Use ‘Edit->New’ to create a new model portfolio. Enter the benchmark name as the portfolio name.
2. Enter the index constituents of the benchmark with their weights. In Portfolio Lab, the index tickers start with ‘$’.
3. Select rebalancing: monthly

Your newly created portfolio can now be used as a benchmark. Whenever you need this benchmark, click Compare option in backtest, then A portfolio, then select your benchmark. You may also use this as a benchmark in the PDF report.
If a particular index is not available, you may also use ETFs as proxies for benchmarks.