Go through the eligibility criteria here and make sure you fulfil the requirements.
You will need to go through 10 e-learning modules at http://www.rcaro.org/elearning/ and be willing to self- certify that you have gone through the material.
You will need to go through the “how to report nuclear medicine tests “ at https://www.anmboard.org/books/ and be willing to self-certify that you have indeed gone through the material.
You will need to certify the level of your English language prowess.