To view seasonality on a ticker symbol on a watch list, make sure you don't have a strategy in the backtest tab, you want to start with the buy and hold chart and set your time frame below the chart to 10Y.
Click on Candlestick and choose Seasonal from the drop-down menu and beside it choose monthly.
Then click on one ticker from the list at a time. It will display the monthly seasonal candles.
Once you mouse over a candle you will see the 10 years of seasonal history of that month.
If you want to pinpoint the seasonal further, you can change to Weekly and select a month.