There are several ways a trade can be added to the Option Risk Analysis window.
Click on the Add Option button in the Main tab of the ribbon menu. An option chain selector for the stock will pop up and let you select an option to add to your list of trades.
You can also click on the Add Underlying button in order to add an equity trade (for example, for Buy/Write strategies).
You can also drag/drop the option to be added from a portfolio window.
Double-click on the trade's data column (for example, Qty or Price) in order to change it.
Trades can be temporarily removed from analysis by un-checking the checkbox on the left of the trade in the table.
Or permanently removed by clicking on the button in its row or highlighting the row and clicking the Remove Row button in the Main tab on the ribbon menu.
You can also clear the whole trades table by clicking on the Clear All button in the Main tab on the ribbon menu.