In the "My campaigns" menu, click on the "Create a new campaign" button at the top left, then fill in the required fields.
The "Next" button at the bottom of the window will allow you to chain actions to fill in all the information relating to your campaign.
Finalize the action using the "Create campaign" button and you campign is now live !
Tip: You can setup campagnes with undefined dates. For example, if you do not set a start date, the campaign will start today. And with no end date, the campaign won't end.