1) On the dashboard click on Campaigns under the Tools section on the left

2) Click on the Call or SMS  button depending on whether your campaign is an SMS campaign or a Call campaign

3) You will need to fill in the Flow name, Caller ID, Campaign Type, and  List of numbers in addition to the time of the campaign 

4) Save the campaign by clicking Add

PS, if you want to send a transactional SMS campaign, you need to create a transactional SMS template and choose it in the "New campaign" popup. This page has more information about how to create SMS templates.