The free version of BikeCAD would be a handy tool for designing your 60cm frame. You can launch the free version by any of the methods described at: bikecad.ca/launching.

While there are different conventions for defining the size of a bicycle, when one speaks of a 60cm road frame, that would generally imply a 60cm seat tube length measured center to center. You can adjust the seat tube length in the Primary dimensions dialog box. Since dimensions are entered in millimeters, your seat tube length would be 600mm.

Beyond that, I shouldn't likely make assumptions about what other dimensions you'll want. The nice thing about BikeCAD is you can make the rest of the frame as big or as small as you like. Having said that, a lot of traditional road bikes would have a horizontal top tube and be square. A square frame is one with an effective top tube length equal to the seat tube length.

In the Primary dimensions dialog box, the effective top tube length and top tube angle are paired as described here. For a traditional square frame, you could enter 600 mm for the effective top tube length and 0 for the top tube angle.

When it comes to actually building your frame, you'll need BikeCAD Pro to obtain the lengths and angles at which to cut all of your tubes.

Good luck with your project!