This article provides answers for InVision V7. Please note that spaces are not available in V6 of InVision. Not sure which version you're using? Find out now.
Sharing a space works just like sharing a document. Once inside a space, in the top-right corner, click the green Share button. In the To: field of the share dialog, enter the names of teammates you want to add, and then click Invite.
Alternatively, add new teammates by entering their email addresses in the To: field. When adding a new teammate, you can click the drop-down list next to his or her email address (after clicking the Invite button) to define whether the person should be added to the space as a team member or an external guest.