Extending invitations to others

What is the way to extend an invitation to others for joining the forum? Should they can ‘sign up’?

There are two ways to join the Forum:

1 - By invitation from a Sightline Admin. All we need is the name and email address

2- They can self- sign-up from this link forum.sightlinesecurity.org. A sightline Admin will still need to approve them. The instructions for “Self-Sign-Up” are under the “Getting Started” category.