According to mira keller, "the death penalty is a cruel and unjust form of punishment."
how can you change this example to better follow the rules of quotations?

Make the “T” in “The” lowercase. This makes the example:

According to Mira Keller, "the death penalty is a cruel and unjust form of punishment."

You should indicate where Mira Keller spoke those words.

Explanation:

You took this information from some research source. This source can be a book, a lecture, a magazine, among others. For this reason it is important that your citation indicate the source of the research, be preceded by a comma, begin with capital letters and be within quotation marks.

Example: Miria Keller, in her speech on the death penalty, said, "The death penalty is a cruel and unjust form of punishment."