how design a beam connected to a column as a cantilever

No offense but the question's probably to vague for us to give you anything other than the most high level guidance. So here's thatL

1) Figure out the forces in the members. Flexure, shear, and torsion predominantly.

2) Design the members as beams, beam-columns, and tension members as appropriate using your local design standard.

3) Pay careful attention to the buckling of things, lateral torsional buckling in particular.

4) Consider a pair of vertical stiffeners in the beam beneath the inverted column (often coined a "hanger").

Feel free to dive in, make some progress, and post updates here. We can help you step through the details as you go.

Consider whether you actually need that diagonal brace while your at it and whether the connections are bolted or welded, and how that may affect local considerations like flange bending etc.

Also pay particular attention to deflection at the pipe, and whether the pipe stress guys can accept it. Given the arrangement you have shown I suspect deflection will be un-acceptably large unless the loads are very small.