You can easily share an application with an existing GovWell user or invite an external collaborator by clicking the 'Share' button at the top right corner of the application page:
A window will appear, allowing you to select the user. If the person is already part of your organization, simply type their name under 'Share with existing GovWell user' to select them. If they are not yet part of your organization, add their email under 'Share via Email'. They will receive an invitation email to sign up for GovWell and join your organization, gaining access to the application with view/edit permissions.