Weird, it sounds like you are just starting out since your question relates to step #2 of Jeff's instructions. 'ltran.html' is a file that is exported from OOTP when you create the games html files. Cato's OOTP History requires you to output the year end league html files (you don't need the player pages) from the game for each year you include in OOTP History.
Here is what Jeff Cato's instructions say regarding this (it is worded better than any of us could say

):
For OOTP4:
2. With OOTP version 4, create the league HTML pages. Player pages and boxscores are not necessary.
For OOTP5:
2. With OOTP v5, create the league HTML pages. Player pages and boxscores are not necessary.
If you have done step #2 already then make sure that OOTP History is pointing to the correct folder where these html files reside. You do that within OOTP History by going FILE --> OPTIONS --> GENERAL TAB --> GAME HTML FILES. That path show go to where the OOTP html files are located.
Some related points to remember:
- Always go through the Cato instruction stages at complete one season at a time or it will not work.
- Make sure you are using the right version of Cato History to go along with the version of OOTP you are using. Also make sure you use the related CommishJoe programs from Jeff Cato's site.
- Although the instruction for Cato's History program are long and complex if you are not computer savvy, they do cover all required steps very well so follow them carefully and with confidence.
Good luck Michael!