App security: installation and code

Hi,

I'm a basic user of Visual Basic and now i'm working on my own apps and i want to know how to have some security to my app, like:

1 - Secure the installation with for example a serial or activity code.
2 - I've heard about the softwares may be decompiled with some tools and the code will be exposed. How can i protect my code??

I don't want to make any complex security because i have no technical skills and is ridiculous to fight piracy, but because i want to sell the software i have to create some kind of security.

Can anyone help me?
Thanks