I started working in April 2017 on F1 CPT and changed over to F1 OPT on May 28 2017. On Oct 1 2017 my status again changed to H1B. How do I file taxes ?

It depends -

Your US filing status will be determined by your visa type and if you meet certain IRS tests - Green Card Test or the substantial presence test . Under your F-1 visa class you are exempt from the substantial presence test  for the first 5 years as a student and if you changed your visa class during the year, you would not count these exempt days under the F-1 visa. If you changed your visa class in Oct 2017, you will still not meet the substantial presence test.

If you do not meet these tests for the first year in the USA, you will be considered a nonresident alien and will file a Form 1040NR which is not supported by TurboTax. Here is a link to the IRS website for Form 1040NR, U.S. Nonresident Alien Income Tax Return.

However, if you are a Nonresident Alien who will become a Resident Alien under the Substantial Presence test in the year following this taxable year, you may elect to be treated as a Dual Status Alien for this taxable year and a Resident Alien for the next taxable year if you meet certain tests. Refer to the First Year Choice area, under Dual-Status Aliens, of Chapter 1 in Publication 519, U.S. Tax Guide for Aliens.

(TurboTax does not support dual status filings.)