The period determines the quantity of data that is used to create the indicator. In a general sense this means that a lower period will make for a "faster" or more responsive indicator whereas a higher period will create a "slower" or more general indicator because it is pulling averages from more data.
You can see this represented by setting up two of the same indicators in two different colors and making their periods very different e.g. 5 and 50.
To adjust the period on an indicator
1. Left click on the chart where the indicator you would like to modify is found.
2. Right click on the same chart.
3. Select "Indicators" from the dropdown box.
4. Select the indicator you would like to modify from the list in the left area of the "Indicator List" dialog box. The highlighted indicator is the indicator whose settings are displayed in the right area of the same dialog box.
5. Scroll down until you find the "Period" quantity bar under "Settings" in the right side of the "Indicator List" dialog box. Click the number in the quantity bar and adjust it how you would like.
Note that the number may be difficult to see as it is black on a grey background.
6. Click "Ok" at the bottom of the dialog box.
To change the color on an indicator see the following article: