I assume you mean 'How to add a new folder for a new MetaClass' in the navigation tree 'Main Objects' of the Windows Front-End Desktop?.
This is regarding customization od navigation trees. Expert work
See technical article http://community.mega.com/mega/attachments/mega/HOPEXV1R2/10/65/HOPEX%20Studio.pdf
HOPEX Studio - MEGA Studio, Configuring Navigation Trees
Maybe you want to configure the window 'Main objects' for all users.
There is no possible configuration for this for all users.
Each user should add it manually using menu 'View > Navigation Windows > Main Objects'
Note that there was an issue recently regarding persistence of this configuration (fixed)