There's no simply way to secure your application from being copied, used, etc. You'll never be sure that your application is not used, no matter of how many ways you used to protect it.
The base idea is very similar to well known solutions: each copy of your application need to get specific serial number (SN). Then, you have to create installer which will:
1) demand user from entering SN
2) connect to your database and check if that SN is already in use
3) depending on result in 2) allow/disallow further installation process.
Note: during the installation process, you have to write an information (hidden to user), for example SN, that an application has been installed properly. If SN does not exists, executable won't run. See:
Where should I store my data?[
^]