To start dialing, go to Live dialer in the left-hand menu. You'll see a list of your active call campaigns, each showing its status. Choose the campaign you want to work and select Start dialing to open the live dialer cockpit for that campaign.
Only campaigns with an ACTIVE status can be dialed. If a campaign you expect to see isn't listed, check with your admin that it's been loaded and activated under Campaigns on your Dashboard.