You can manually add a contact to an automation from the contact’s record.
Once you open the contact record, find the Automations section and click the “+ Add” button. From there, you can select the automation you would like to add the contact to, and click “OK.”

For more help adding or removing a single contact from an automation, read this Help article.
You can also add or remove a specific group, or segment, of contacts from an automation. Read our guide to ActiveCampaign’s segment builder to learn more about segmenting contacts.