To create a tangent line to a 2D spline curve in Pro/Engineer Wildfire 2, users should utilize the tangency constraint found in the constraints box of the sketcher menu. However, some users report issues with the spline not being detected by the tangent constraint, complicating the process of creating a circle tangent to the spline. Additionally, difficulties in placing a point on the spline curve have been noted, indicating potential limitations in the software's functionality. Alternative methods for achieving tangency may need to be explored if the standard approach fails. Effective solutions for these challenges remain a topic of discussion among users.