Hi SRR! Happy to help you with this
You're correct that you're supposed to accept the premises as true, but this is different from circular reasoning. Circular reasoning means that the author's conclusion is identical to the premise offered to support that conclusion. The author of the stimulus uses circular reasoning because the conclusion of the argument (if you lack self-understanding, you can't understand others) is just the contrapositive of the premise (without self-understanding, you cannot understand others). A conditional statement and its contrapositive are identical in meaning.
This reasoning structure is different than a common valid conditional argument structure, which is the following:
Premise 1: If A is true, then B is true.
Premise 2: In this case, A is true.
Conclusion: Therefore, B is true.
In this valid reasoning structure, a conditional statement is offered as a premise and is then used to make a conclusion about whether a certain situation is true. By contrast, in the stimulus, the author offers a conditional statement as the premise of the argument, and instead of using it to draw a conclusion about whether a certain situation is true, they simply state the contrapositive is therefore also true. But remember that the contrapositive of a conditional statement is always true and is just a restatement of the original conditional statement. As a result, this would constitute circular reasoning.
To sum up, because the conclusion is just the contrapositive of the conditional statement offered as a premise, the argument uses circular reasoning. The contrapositive is just a restatement of the conditional statement, so the premise and the conclusion are identical in meaning. This is different than a valid argument structure that uses conditional reasoning, which would use a conditional statement to demonstrate that a given situation must be true.
I hope this helps, and let me know if you have any other questions!