So sorry about your Father's passing.
The only way to access your Father's account is if you know the login information he used (user ID and password). If you know that info, post back in the comments section here and someone in the forum will instruct you on how to proceed.
However, you can get a transcript (abbreviated version) of your tax return by using the IRS webpage linked below.
https://www.irs.gov/individuals/get-transcript
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***