@ES and I just met today. Thank you again, Emna! 

She shared an important observation. The Import button on the xStudio homepage allows 3DXML only. 

Actually @DG asked a similar question in July. 

Yeah, indeed, a natural idea on the first step before rendering is to import 3D models to xStudio. 

However, the process works a bit differently on the platform😅 

Apart from software user experience improvements in the future, let me clarify the mechanism a bit to get you started easily. 

The intent of 3DXML is to transfer data between 3DEXPERIENCE platform tenants. So the xStudio or xHighlight (non-modeling Apps) Import button here assumes you've got 3DXML production made by the platform already. It doesn't import other generic formats. 

On the other hand, to import a wide range of CAD models to the platform as the first step, xDesign or xShape (modeling Apps) is responsible to bring them to the 3DSpace, hence the Import File button as shown below. 

The supported format list is pretty long . Please make sure to scroll up and down to find your preferred format, e.g. Stp at the bottom of this list. 

Also pay attention to the Destination, as you may not want certain models in a public space. 

Once the data is imported to 3DSpace, all the roles/apps can access them and take it from here. For instance, xStudio can create a new production from an existing model for high quality rendering. 

Hope it helps. 

-Oboe