Hi!
For OTA you don't have to give maths paper!
So you have ample of time to study. The other two papers are English and general Sciences.
For English this are major topics that have been asked in past.
Spotting Errors Questions
Sentence Arrangement Questions
Synonyms & Antonyms
Selecting Words
Ordering of Sentence
Comprehension Questions
Ordering of words in a sentence
Fill in the blanks questions etc.
The questions are pretty basic not of very high difficulty. Read newspaper as much as you can, I'll suggest read The Hindu paper. It will cover your current affairs and Vocabulary.
For General sciences read as much as you can on History, Polity, current affairs and PCB if you can! Practice General Science topics as much as you can! Make sure you get above 30 marks.
Practice Hard!
Good Luck!