Slicing

I just loaded cura 15.04 on my lap top.do I need to add a slicing program or has it come with curator?

Cura is your slicer.

O.k. Thanks.one other question,I can't print from the cura program on my laptop.any ideas?

The "Model Path" if you will is as follows

3D Model in .STEP (such as from Solidworks or Autodesk) > Mesh in .stl (such as a thingiverse file) > Gcode in .gcode (from cura) > Instructions to printer in .gcode (from matter controller or similar) > Movement of motors (controlled by firmware) > Printed Object

The program that sends instructions to the printer is typically referred to as the "Host Software" Examples include:
Mattercontrol
Craftware
Repitier
Octoprint
Slic3r?
and more.
I suggest that you see the wiki for further details and best of luck.

Slic3r isn't a host. It's, as the name would suggest, a slicer. I've only seen Cura a couple of times, but I think it has some host capabilities as well. If the electronics have a web interface, a host isn't strictly needed.