In which way one can edit the core files

[sjferrari]

Hi,

 

I am working on the PrestaShop version 1.6.1.1 and I found that in the code base, almost all the files contain a DISCLAIMER not to edit the file. 

 

My questions is though I wont need to change anything in the class files but for the theme files(.tpl) files, I have to rather apply some hooks and add some custom code. Is there any other possible way to do this or customization in theme files is possible.

 

Please help me on this. Thanks in advance.