Quick Leader

The Quick Leader dimension is used to create any dimension that there isn't a specific tool for already, and where you need to enter a lot of customized text.  To use the Quick Leader dimension, click the icon and select the line that you want the dimension arrow to be on.  From here, you can create as many leader line segments as you wish.  Usually you will want only one or two segments leading to your text.

Once you have the leader lines positioned as you want, hit enter to begin entering text.

 
When you begin to enter text, the command line will ask you for the first line of dimension text, then next line, etc...  AutoCAD will not create any kind of text box or way of automatically creating a new line of text.  You must tell it what you want to appear on what line, or it will all get put in one continuous segment on the first line.  When you are done, hit enter to confirm the text.