If you’re on the SOLO Plan then only you can login to access your Projects.
If you are on the PRO or ENTERPRISE plans then you can have unlimited team members logging in to collaborate and work on the same or different projects at the same time.
To upgrade from the SOLO to PRO plan just go to Smartspec > Settings > Account Details and you'll see the upgrade link under Plan & Usage.
To invite team members to your PRO or ENTERPRISE account just go to Smartspec > Settings > Users then click on the Invite New User button.
Enter the name and email address of the person(s) to whom you would like to send the invite. They will receive an email invite to join your account, and after they follow the link within the email and enter a password, they can start using Smartspec.