That should be a pretty simple straight forward configuration. Do you have email confirmation and/or admin approval enabled? That'd change things a little bit since you'd probably want to wait for them to be confirmed and/or approved before forcing them to join. The below for example is without confirmation or admin approval.
Registered
Global
Triggers: onAfterUserRegistration
Type: CB GroupJive
User: Automatic
Access: Everybody
Action
Mode: Join Groups
Groups: SELECT_GROUPS_HERE
That's all there is to it. They'd be placed in whatever groups you selected after they register. If you have confirmation and want to wait for them to be confirmed you can use the below. Basically just a trigger change with a condition to ensure confirmation state is switching to confirmed
Confirmed
Global
Triggers: onAfterUserConfirm
Type: CB GroupJive
User: Automatic
Access: Everybody
Conditions
Field: Custom > Value
Custom Value: [var2]
Operator: Equal To
Value: 1
Action
Mode: Join Groups
Groups: SELECT_GROUPS_HERE
Now when they confirm their email they'll be placed in the groups instead of directly after registering. If you have moderator approval it's again just a relatively simply change. Is actually just a literal trigger change from the above.
Approved
Global
Triggers: onAfterUserApproval
Type: CB GroupJive
User: Automatic
Access: Everybody
Conditions
Field: Custom > Value
Custom Value: [var2]
Operator: Equal To
Value: 1
Action
Mode: Join Groups
Groups: SELECT_GROUPS_HERE
Now when you confirm their account they'll be placed in the selected groups.
Note you only need to use one of the above. Don't use all 3. Which you use is entirely up to you and your configuration.
PS: We inaugurate our community site tonight, I added your name in the credits
I appreciate it, but no need to credit me personally. We're a team here so if you do want to credit us just credit Joomlapolis. 😊