On the ribbon, click Annotate tab Dimension panel
Baseline
.
Alternatively, on the ribbon, click Annotate tab Dimension panel
Baseline Set
.
Select the geometry to dimension in the graphics window :
Right-click and select Continue. Move the cursor to preview placement of the dimensions.
Autodesk Inventor assigns a point on the first of the selected edges as the origin.
To specify a different origin, right-click the dimension extension line that you want to assign as the origin and select Make Origin.
Click to place the dimensions.
Right-click and select Create.