Check the threads referenced here: UNV import to support line element (beam) - #12 by FEAnalyst
This tutorial may also be helpful: https://youtu.be/AiLCzKAOdx0?si=is62sOoSHkigEcr9
However, in CalculiX, solid and spring elements and even MPCs themselves are more commonly used to model beams than beam elements due to their various limitations/bugs (even though beams are likely the most common choice in other software).