Use Blender - it's completely free and a very comprehensive package:
The Freedom to Create
www.blender.org
Then start with their tutorials:
Home of the Blender project - Free and Open 3D Creation Software
www.blender.org
Then go through some YouTube videos:
Most important part of all of this? Practise and not just with Blender. Constantly practise your artistic skills: doodle and sketch simple things, as often as you can. Practise drawing faces, hands, feet, knees, buildings, doors, chairs, mountains, clouds, pebbles, and so on. Practise different styles, use different materials, different textures. Practise when you're tired, angry, hungry, happy, refreshed.
Do all of this, as much as you can, and you'll soon learn and understand
what you want to create in Blender; the
how is pretty easy to pick up.