Dear demo,
I've solved the problem in this way: first it is necessary to enable the admin role to create documents. You have to go in the 'Roles Management' section under 'Profile Management'. Here you have to activate the authorizations for the admin role: for this role it is important to activate the 'Create Documents' authorization. Then if you log out and log in again with the credentials biadmin/biadmin you will see the 'My Analysis' tab in the workspace.
Before creating any documents remember to add at least one data source and to flag the option 'Use as cache' in order to have one data soure used as knowage cache.
I hope you find this information useful, but if you were looking for something different, please answer again!