How do I go about learning the models

Depends on what you want to model and how much you're willing to put up with a learning curve.

I personally like Blender (blender.org) and MoI (moi3d.com).

Blender:
- good for polygon model (here's a cube, pull out face, split face into more faces,  etc.)
- ok for sculpting (like here's a block of clay, you have various tools to carve and pull to deform the clay blob)
- very powerful
- lots of plugins
- very active community
- open source & free
- a lot of great tutorials online (I personally use: cgcookie.com/blender for my tutorials)
- downside: steeper learning curve, not the most friendly UI -- though, a lot of people give it crap because there are hotkeys you need to remember (eg "g" for grabbing/moving an object), but (a) you can just press the spacebar and type in the command if you can't remember the hotkeys and (b) once you remember the hotkeys it makes modeling really fast.. in other apps I usually end up setting up my own hotkeys anyhow

Moments of Inspiration or MoI for short:
- good for NURBS modeling (draw a vector path, extrude it, bevel the edges)
- UI is pretty simple
- also scriptable
- there's one guy doing the development so updates are slower, but he is very active on the forum.. I've always gotten response from him to my questions on the same day

If you want something that's easier to pick up, you can try SketchUp (though I've always had trouble exporting SketchUp models to print).

I also recommend going on Thingiverse (thingiverse.com), finding a model you like, importing it into Blender/MoI/Sketchup and tweaking it. A lot of times there's no need to create things from scratch. There are some pretty cool stuff on Thingiverse that you can use as a base template.

Is that somebody in this forum?

No, you asked how to print sneakers, so I said sneakily. Just playing with words.

P.s I really need the help