Calculate and apply concentrated force at specific nodes in accordance with your cable profile.

You can not calculate the forces applied to the deflection point. because there are slipping of cables. You can model the cables as beam element that does stand as the axial stress and then model slipping of cables to the deflectors. for more information you can read my publications

You can calculate the equivalent external forces produced by the post-tensioning process and apply it as at the nodal points.

Calculate the prestressing force that will develop in the external tendon and then apply it at the two appropriate nodes (as per your discretisation) following the cable profile at that point.

First you add truss members that match the tendon geometry. Then you add roller supports  at the junctions allowing displacements along the tendon line and pin supports at the anchoring points. Next you apply to all truss memebrs a negative temperature difference that induces the prestressing force. (F=EA α DT) where E the Young's modulus, A the area of truss member, α the coefficient of thermal expansion (10e(-5) for steel - (but you can put anything in this case) and DT the temperature difference. If you want further to add specific friction forces at junctions you can do it by adjusting co-linear springs of certain stiffness.