I am not sure what those white dashed lines mean. However, The crossed purple lines show you where the origin is: righ in the middle of the part.
Lift the spindle up a bit, well clear of the part, Zero it up there, stick a bit of 1/8" PVC welding rod in the chuck, drop the feed down slow (slider), and push the Go button. This is called 'cutting air', and we all do it!
Before you do, click on ToolPath (tab 3) and see what the movement limits are. Make sure they won't cause grief.
Cheers
Roger