How to implement enhancement for a customer exit?

Hi Friends,

I am enhancing a customer exit for first time.

Can you please help me how to create an enhancement.

I want to write my code inside customer exit EXIT_SAPLCOZV_001 and include ZXCO1U06.

Now i cannot write code inside include ZXCO1U06.

I read somewhere that after creating enhancement i will be able to write code inside this include ZXCO1U06.

Help will be greatly appreciated.