If DesignCenter is not already open, click
View tab > Palettes panel > DesignCenter.
Find
On the DesignCenter toolbar, click Tree View Toggle.
In the tree view, navigate to the drawing that contains the block definition you want to insert.
Expand the list under the drawing and click Blocks to display images of the block definitions in the drawing.
Do one of the following to insert the block:
Drag the block image into your current drawing. Use this option when you want to insert blocks quickly and move or rotate them to their precise locations later.
Double-click the image of the block that you want to insert. Use this method when you want to specify the exact placement, rotation, and scale of the block as you insert it.