I was never offered healthcare coverage from my employer. What do I do?

It sounds like you may owe a penalty for not having health insurance.  There is nothing you can do about that, unless you qualify for an exemption:

https://www.healthcare.gov/health-coverage-exemptions/exemptions-from-the-fee/

You can get non-employer health insurance, such as a private policy through an insurance company, or a plan through the Healthcare Marketplace.

https://www.healthcare.gov/