quick help about CI beginning steps

[eluser]naom[/eluser]
Hey, I need some quick help about installing CI and beginning steps.

I am currently working on a series of websites coded with CodeIgniter. I want to set up another website which is similar, but with different design and using a different database. I am planning to use the code which exists for the current websites and just edit what I need to for building this next one.

Will it work to simply copy and paste the directory on the other sites and edit what I need to, or will I need to install CI first? Please let me know and it'd be great to have any tips you may have.

Thank you!
Naomi