First, download Blender. Easy step. https://www.blender.org/download/
If you have mac, choose mac. If you have windows, choose windows. Also, if your computer runs 32 bit, choose 32 bit. If it runs 64 bit, choose 64 bit. You can find out which bit your computer runs by typing in your search box, "system information." If you have windows 10, you can just type, "about your pc."
Also, if you do run mac, you should probably buy a mouse as it will be more easier to use than without one. It's alright if you don't have a mouse for mac.
Here are blender's requirements for what is average and what is best for your pc to work with blender:
Minimum (basic usage) hardware
32-bit dual core 2Ghz CPU with SSE2 support.
2 GB RAM
24 bits 1280×768 display
Mouse or trackpad
OpenGL 2.1 compatible graphics with 512 MB RAM
64-bit quad core CPU
8 GB RAM
Full HD display with 24 bit color
Three button mouse
OpenGL 3.2 compatible graphics with 2 GB RAM
Optimal (production-grade) hardware
64-bit eight core CPU
16 GB RAM
Two full HD displays with 24 bit color
Three button mouse and graphics tablet
Dual OpenGL 3.2 compatible graphics cards with 4 GB RAM