Once you click More Trendline Options, a window will open that allows you to select the type of Trendline and options related to its calculation, display, and appearance.If you selected a basic option you are done, otherwise continue to Step 3. You can select a Trendline option from the drop down menu or, if you want more control over the Trendline, click More Trendline Options. Three tabs should then appear, go to the Layout tab and click Trendline.Select the desired chart by clicking it.Basically, this is mostly used as a visual aid to illustrate an upward, downward, or flat trend over varying data points in a chart. Trendlines allow you to show trends in charts that might be otherwise difficult to notice. How to add, manage, and remove trendlines in Excel
