Here's a very good guide from GOV UK:
https://www.gov.uk/guidance/keeping-your-domain-name-secure
It's written for domains under gov.uk, but, ignoring that, the rest is universal and thorough.
It's written for domains under gov.uk, but, ignoring that, the rest is universal and thorough.
You may need to switch to a registrar that will let you do it, but that's generally a matter of finding one and giving them enough money, which isn't really difficult. Look for a corporate/brand focused registrar and call their sales and see what the minimum spend is.
If the registry for your domain doesn't do any registry locks, then you would need to switch to a different TLD, which is difficult.