
Create the points needed to define the coordinate system. Three points are needed for the origin, the direction of the first axis from the origin, and the general direction of the second axis on the (first axis, second axis) plane. Create the points by using Insert > Control Point, Insert > Topological Points, or other geometric construction point interfaces.
Control Point in the Common User's Guide

Click CSByPoints on the Geometric Construction Palette.

In the Assign Axes To box, select the initial axes and plane to define.

In the Coordinate System box, select Direct.

Select the origin point.

Select the point for the direction of the first axis.

Select the point for the general direction of the second axis.
A preview of the coordinate system displays. The direction of the third axis is determined by the righthand rule.

If the third axis is not in the needed direction, select Indirect in the Coordinate System box.
The direction of the third axis flips.

Click Continue.
Temporary geometry displays in the graphic view and as CSByPoints in the Geometric Construction Explorer.

If needed, create additional geometric constructions.

Click Close to return to the main command ribbon.
The geometric constructions are not created and saved to the model until you click Finish on the main command ribbon to create the model object.