If you want to grant others access to your servers and applications, you need to create a Company. Per default you only have a Personal space, here it's not possible to invite users.
To create a company click Settings and create a new company.
When you have created a company, you can click your name to select the company
When you have selected your company, you can invite users under Settings
Right now it's only possible to invite users that already have an account, this will change later.
When selecting a company, you will only see servers and apps for that company, and when creating a server, it will only be created under that company.