Go and create a page as a regular page and be sure that you have the Visual Composer installed and activated
If everthing ok you should be able to see the Visual Composer logo and menu on top left of page editor just under Page Title
Click Backend Editor option and you can start
To use Phoenix elements in the page builder, first fire up the page builder on your page editor, then click the top left button "Add element" to pull down the elements menu. all Phoenix menu elements are in sections marked "Theme elements"
You first need to add a row that will hold all your other elements and start build content by just adding elements to this row
Check our youtube channel for a quick tour