All fighters, managers, companies, events and just about any other item within the game, have an ID number.
You can find this number in brackets on the appropriate profile/homepage. e.g. if a fighters name says Chuck "The Iceman" Liddell (4532) then his ID would be 4532.
We suggest using tabbed browsing to make your life easier, when trying to find a particular ID number. Have the page you were working from open in one tab and then open another tab to search through the site to find out the ID number you are looking for.