In the Draft environment, choose Home tab→Annotation group→Callout 
.
Note:
In a model, the Callout command is located on the PMI tab→Annotation group.
(Specify callout content) In the Callout Properties dialog box, enter the callout text and select any special characters you want to display in it.
You can enter any combination of plain text and associative property text using these techniques:
Type plain text. You can add property text to a plain text string.
On the General page, click symbol buttons to specify additional information to display, such as the diameter symbol and the depth symbol.
Copy hole callout strings from the Hole Callout page, and paste them into the text boxes on the General page.
Add associative property text by doing any of the following:
Click the Property Text button 
to select associative properties using the Select Property Text dialog box.
Type three-character property text codes for the symbols you want to insert.
The Preview button at the bottom of the dialog box opens and closes a window so you can see the effect of your changes as you make them.
Click OK to accept the changes and close the dialog box.
Specify formatting options for the callout text and border.
Example:
On the Callout command bar, you can:
Select Show Border to display a border around the callout text.
Click Border Type, and then choose the Fit to content option to automatically match the width of the callout box to the width of the callout text, even when the content changes.
Use this option to ensure drawing title property text always fits in a fixed-width title block cell.
On the Border page (Callout Properties dialog box), you can control the behavior of callout text within the callout box. Use the options under Gap between border and text section to control horizontal and vertical spacing inside the callout box.
Click an element or click a point in free space to place the callout.
Tip:
You can use the Callout command to automatically dimension thread references.
You can place a callout without a leader by clearing the Leader option on the command bar.
You can control whether a callout is above, or embedded in, a break line using the Position option on the command bar.
You can double-click a callout to edit its properties.