The question is “How to find Category ID in wordpress ? ” see the pictures below :

click image to enlarge

Point your cursor to one of your category at your Manage Category administrator and see of the bottom your screen at status bar. You will find the category ID then put them in the code.

Example:

Manage Category ID under index.php : in the CAT SECTION TOP LEFT/RIGHT, CAT SECTION MIDDLE LEFT/RIGHT,CAT SECTION BOTTOM LEFT/RIGHT you will find this code :
……$display_categories = array(1->THIS IS CATEGORY ID-CHANGE THIS VALUE);……..

and you will customize another files to customize ID categories. Let me know if you need question.