Wealth-Lab generates an out-of-memory exception message when I try to perform a portfolio backtest on a large daily database (2100+ stocks). I have turned off some extra Performance Visualizers and that has helped, but I read online that I should also try clearing the internal cache at the end of my strategy, but I don't know how to implement the advice "call Bars.Cache.Clear at the end of your strategy to explicitly clear the internal cache that stores DataSeries and free memory". I can't find the proper syntax to use. Help?

Clear is a method, so it takes an [empty] parameter list:
Bars.Cache.Clear();

It might help if you create lots of indicators, but the best bet for large simulations is a 64-bit O.S. and lots of memory.