In the Contacts module, select the contacts you want to add to the Drip Campaign by checking the box next to their names.
Add to Drip Campaign
Click the Menu button and then click Add to Drip Campaign.
Select Campaign
Select the campaign to which you want to add the contacts, and then click Save.
That's it! You've added the contacts to a Drip Campaign. If the campaign's first step is set to Immediately, it will be executed the moment you add the contacts.