How can I write in my autobiography about my anger towards my dad for not letting me cry at my great aunt's funeral?

Nice to read that you are finally writing the book.

Relive the moment and write it all down. You are at the funeral. You want to cry because [say why]. Your dad won't let you cry by [say what your dad did].  You felt anger. What did you do?

BTW, How do you intend to write your autobiography if you need to ask strangers advice about expressing your emotions? We are not you. We did not live your life with you. You are you and you intend to tell us about your life.

You don't need us to tell you to write down what you felt. Just be honest.

You can attempt to write it as a metaphor. Here's a passage I thought of. Hope it helps. 

As if standing in a funeral hall full of distance cousins and relatives drowning in self-loathing isn't bad enough, I began to feel the same emotionally draining floodgates open within me. My father turned to see the tears in my eyes and gave me the most stern expression I've ever seen my father portray. "Don't cry," he whispered to me with undertones of anger and frustration. That's when my sulking stopped. My teary eyes froze, turned to ice, and began melting off my face and sizzling into my skin at the heat of my rage towards him.

The same way you wrote your last book: You spend a year or so asking about fonts, spacing, margins, sizes, word count, pages, and software. You don't start writing yet! That's not the most important part in the process of writing a book! Once you're done with all the technicalities, you spend another year writing the preface. Spend two years, if needed! Because this is the most important part, no reader is going to skip it. In between, you fantasize about diaper changing. Rinse and repeat for your next book.

Good luck! 

What, ANOTHER book that you're never going to write?

Just write what and how you feel. The words will come to you.