Attach a Reference File - Xref

View tab > Palettes panel > External Reference Palette

 

Insert tab > Reference panel - Small Arrow - External References

 External Reference palette > Attach DWG

Navigate to the file location - Open

Set the options as need

Reference Type: Attachment or Overlay
You can set the Scale, Insert Point, Rotation
Path Type: Full path, Relative path, No path
Block Unit: The Insertion Scale units of the reference file can be control by Unit command