To open the Dimension Style Manager, click the dimension with the paintbrush icon on the expanded Annotation panel, as shown in the following screenshot, or use its command alias, D:

The Dimension Style Manager window will open with a list of standard dimension styles in the left panel, as shown in the following screenshot. The dimension styles in your case might be different if you have another template, but that won't matter here as we will be making our own dimension style:

Click the New... button and give your dimension style a name. I will call it Sample Dim for our example. From the Start With menu, select the Standard dimension, make sure the Annotative checkbox is not selected, and click the Continue button. This will make a copy of the Standard dimension style and name it Sample Dim, which we will modify:

A new Dimension Style window will open with lots of tabs and panels. We will look at these options and how they affect our dimension style. But before we go further, let's familiarize ourselves with dimension terminology using the following screenshot:

Now that you are familiar with the terminology used for dimensions, let's start with the Lines tab of the Modify Dimension Style: Sample Dim dimension style. All the changes you make to the dimension style will show up in the Preview panel of the Dimension Style window, which shows a sample drawing and its dimensions in the top right of the window.