Choosing parameters allows you set your indicator parameters as desired (i.e. to set the number of periods a moving average is calculated over)

If an indicator has a + sign to the left of the indicator you may click on the + sign to show the indicator’s parameters. To modify the parameter or parameter range, press the Modify Parameter button or double click the parameter or parameter range.
If an indicator has a ‘ sign to the left of the indicator you may click on the ‘ sign to hide the indicator’s parameters.

To set or replace the currently selected parameter:

1. Select the Set Parameter button.
2. Press the Finish button to end the wizard and add the indicator.

To modify an indicator, data stream, or numeric parameter:

1. Select the indicator, data stream, or numeric parameter to be modified.
2. Select the Modify Parameter button.
3. Press the Finish button to end the wizard and add the indicator.

For information about an indicator:

1. Select the indicator for which you want more information
2. Press the Indicator Help button

The Save Indicator and Modify buttons described below may not be visible depending upon the currently selected Indicator Wizard Interface Options. Press the Options button to change the Indicator Wizard Interface Options. For more information see Indicator Wizard Interface Options.

To save an indicator as a custom indicator:

1. Select the indicator to be modified
2. Press the Save Indicator button (or the Modify Indicator button if you have previously saved the custom indicator).

(DayTrader Only) To eliminate large indicator fluctuations due to the gap between a days opening price and the previous days closing price, select Don’t calculate indicator(s) across day boundaries. When this option is selected, none of the previous days values are used when calculating the indicator(s). As a result, an indicator like MovAvg(Volume,5) will not produce a value until the 5^th bar of the day when this option is selected.
Notes:

• If you specify multiple parameters, more than one indicator will be created. To specify multiple parameters, separate each value by a comma (or semi-colon if the windows regional settings are set such that a semi-colon is the standard windows list separator). For example, specifying a moving average size of ‘5, 10, 20’ will create three moving averages.
• To specify a range of parameters separate the start of the range from the end of the range with a colon. For example, specifying a moving average size of ‘5:10′ will create moving averages with sizes of 5,6,7,8,9, and 10. You may also place an increment value after the end value, again separated by a colon. For example, specifying a moving average size of ’10:20:2’ will create moving averages with sizes of 10, 12, 14, 16, 18, and 20.
• (DayTrader Only) Be careful when using the Don’t calculate indicator(s) across day boundaries option for indicators having a large lookback window relative to the number of bars per day. For example, if this option is applied to the indicator MovAvg(Volume,40) on an hourly chart, no values will be produced as the lookback is larger than the number of bars on any given day. When used in predictions and trading strategies, this problem may cause the prediction or trading strategy to trade only a few bars per day or possibly not trade at all.

 
Topics of Interest:
What are Indicators?
What are Custom Indicators?