Just remember to sign up within 6 mos. of your 65th BD, or you'll be penalized. If you already have insurance, make sure they send you the forms to change your plan so that Medicare is the first payor and the private insurer now becomes the second payor.
Signing up on the website is easy.
Our insurer was rather dilatory; we didn't get our forms until 5 weeks before the BD dates. But everything was processed in time so the transition was seamless.
Due to COVID and the USPS slow-down, I would complete the forms and mail them back ASAP after receipt, however.