There are three ways your community members can join groups in Heartbeat:
Join a Group through Onboarding
Before members can add groups through the onboarding flow, admins will need to set it up. Go to the Settings > Onboarding Setup, and then click Add Group in the Groups section.
Check out this article to learn more about setting it up: https://help.heartbeat.chat/en/articles/5905906-customize-your-onboarding
After you've set this up, when a member goes through onboarding, they will be prompted to select a group or groups.
Join through My Groups
Members can view the groups they are part of and/or join joinable groups from their Settings > My Groups.
Join through Threads
Admin can create a post inviting members to join a group. To do this, type in $join and then select the group you want to tell members about.