This is the summary page of the follow-up campaign, you'll be able to activate it on this page
When you've finished editing/creating your follow-up the last step is a summary where you can find all the information that you've set earlier.
You can return to the previous steps without losing any data.
If you don't want to active your follow-up now you can just click on the Save as draft button, this will save it but not activate it.
Otherwise, you can click on the Activate button that will activate the follow-up.