I don’t know what to do to subscribe to the podcast

I would assume you must have at some point set a Restriction on explicit podcasts, using the method described in section 6 of this page:

https://www.tomsguide.com/us/set-iphone-restrictions,news-21258.html

So you should be able to reverse the process. You may need the passcode you set when you enabled the restriction. If you can't remember the passcode you will need to erase and restore the phone in iTunes: if you restore from a backup if must be from one made before the restriction was set or you will be back where you started.