Normally it should start as default. If not, it might be that the version of FreeCAD you have there is too old... The startpage is there since 0.12 IIRC. Have you tried using our PPA? From there you can get a bleeding-edge development version with all the new stuff ( https://launchpad.net/~freecad-maintainers/+archive/freecad-daily )
Otherwise, you can force it by setting the start workbench as default in the preferences.
How do I get FreeCAD to start up with that helpful welcome page that
comes up when I run it on windows?