Enroll preview counts how many leads will enroll and how many will be skipped before you enroll. Open it first so exclusion rules are not a surprise after the list is in the campaign.
Open enroll preview
Open the campaign.
On Settings → Audience, pick the person list if it is not set.
Confirm Settings → Exclusions matches the skip rules you want.
Open enroll preview. Do not enroll yet.
The preview line reads "{total} leads in {list}: {willEnroll} will enroll, {skipped} will be skipped."
Read the counts, then enroll
Skipped leads are usually already in another campaign, already messaged by another sender, missing LinkedIn, or caught by one of the three exclusion toggles. Change Schedule or Exclusions only if those settings are still unlocked. After launch, select Edit campaign to change senders, schedule, or exclusions.
Read will enroll and skipped.
Change exclusions or the list if the skip count is wrong.
Open enroll preview again.
Enroll when the counts look right.
You can still enroll leads on an Active campaign. Sequence sending follows the schedule on Settings → Schedule. Preview again after any exclusion change so the skip count stays honest. Enroll does not launch the campaign. Launch still happens on Review.