Giving other users access:
Click any project, website or account in your dashboard and click manage users. Depending on your rights you can now invite other users to your project / website or account.
Remove rights for a user
Click any project, website or account in your dashboard and click manage users. Click the red cross on the user you wish to remove the right for.
Get an overview of shared rights
Go to users located on the left menu on the dashboard. Your can now see the users you have given access to. Click the user and then manage rights to edit what rights they should have within your account.