Dear salam.a.alrubaye,
if the approximation using symmetry like in the Tutorial example (Shear Beam) is not good enough for your problem, you probably need to model the whole beam (or use the vertical symmetry plane parallel to the beam axis).
Then, it depends if your loading mechanism in reality enforces 2 identical displacements (then, prescribe 2 identical dispalcements inyour model), or 2 identical forces (then, approximating with 2 identical displacements may or may not work well; if not, use 2 equal forces + the Arc Length solution methods, see also Troubleshooting, 2.4.6.1 Solution methods).

Regards.