There's multiple ways to invite your team members. Before you invite someone to a project you have to add them to your team's workspace. You can do this in the sidebar on the bottom left by clicking "Invite people". You can invite people via email or you can share a link with them.

Once your teammate is part of the workspace you can invite them for each project separately, by default they are not a member of any of the projects. In each project there is an "invite" button in the top right corner where you can invite your team member.

In the top right corner next to the invite button you can see exactly who's part of the project. They can view and edit everything within the project.