The Application Catalog serves as the central repository for applications in all formats. You use Application Manager to manage your applications and their deployment types in the Application Catalog. Tasks you perform to manage your Application Catalog include importing applications and packages, setting up automatic package import, organizing packages into groups, viewing and editing application and package data, and viewing reports on Application Catalog data.
Please refer the following help document which will provide you more information on Creating New Application Catalogs Using the AdminStudio Interface:
Please refer the following help document which will provide you more information on shared default Application Catalog:
When this option is selected, the Application Catalog you are trying to open or create will become the default Application Catalog (and be recorded as such in the AdminStudio Shared directory).
If the Application Catalog is made the default, all other AdminStudio users that use the same shared directory will automatically connect to the default Application Catalog when AdminStudio is launched. Therefore, you should only set this option if you want to affect all AdminStudio users who access that shared directory.
The below video has step by step process which will guide you on how to create a New Application Catalog and then how to make this created catalog as a default shared Application Catalog. Also attached the video for reference.