You will find your existing Facebook campaigns in the "Manage Campaigns" tab.
You will see your campaigns in the left hand sidebar.
To see your paused campaigns, make sure you have selected "show paused campaigns" in the sidebar.
If you can't see your camapigns please click on the "Refresh" button in the upper right corner and select "Ads and campaigns".
If you have many campaigns in your Facebook Ad account this might take several minutes.