Add dimensions in isometric drawing views

On the ribbon, click Annotate tab
Dimension panel
Dimension
.
In the graphics window, select the geometry and drag to display the dimension. Click Spacebar to toggle between inferred annotation planes.
Optionally, use the context menu to select the annotation plane:
- Select Dimension Type
Horizontal or Vertical dimension type to align the dimension with the coordinate planes of the model.
- Select Dimension Type
Aligned to align the dimension geometry with the selected objects in the drawing view.
- To place the dimension on a model work plane, select Annotation Plane
Show All Part Work Planes (or Show Visible Part Work Planes). Then select a work plane in the graphic window. (Available only if the selected model geometry belongs to one part)
- Select Annotation Plane
Use Sheet Plane to place the dimension on the drawing sheet plane.
Click to place the dimension in the appropriate location.