I opened it in assembly design and then in DMUoptimizer saved it as model and reopened it but couldnt paste its copy in part design ;I faced this error:'"paste is not possible""
, I think you can create a copy of this model, as the same I made it, please check the picture that I attach you, and in a catproduct assembly the model and add a new part and change the name with your name for example, and try to start to project lines with the edges, and if you have questions, just let me know, you can use surfaces or solid module.
Thanks for your response but as I said before I had tried this solution but didnt worked ,any way I found a way that worked for me: I opened it in "Geomagic Design " soft ware and saved it as "dot igs" and then opened it with Catia.
I think that copying may have gone wrong. I have already imported several STL files in catia in this way. There is also a rapid prototyping tool in catia. But currentl i use blender for such problems.