I am sorry to hear you failed the exam.
There is no retake policy, which means that in theory, you could have retaken the exam on the very next day, but usually that is not practically possible due to the wait time for the results and the formalities involved in re-registering.
If you wish to re-register, just go to the RHCSA exam page, select your country (if it isn't already selected), and click "Get Started".
All the best in your next attempt!
When I took RH342 I failed it the first go round, but I went back to the email I received that says, "You've unlocked an exam", and used the same process to register again.
In that case I passed it on the 2nd go-round.
When I took DO280, I failed it twice, and could not take it again until I get a new subscription.
Hope this helps.