You can create new model containers directly in your project tab. For that, follow the following steps:
Open the project and navigate over to the Containers tab
Click on the New Container button next to All containers
A new model window will pop up where you will be required to provide the following information:
Model name (127 character limit)
Model Units
Model Category (type)
Model Description (optional field)
Model Code (optional field & alpha-numerical values only)
Press the Create Container button
Optional
If you have already uploaded a file that doesn't have a container and wish to create a new one, you can do so by writing the name of the model container in the Pop-up window Prepare files for upload. To learn how to upload files to the model container, head over the Model upload article.