After logging in to your account, open the Settings ⟶ Users screen on the left side.
With this screen you can manage users added to the workspace.
Click the Invite button in the upper right corner.
Type the e-mail addresses of the users you want to send invitations to in the pop-up window and send the invitation with the SEND INVITE button.
To complete the user addition process, complete the payment process steps from the ongoing pop-up window.