Transferring a Heroku app to Domain

Question

I am a relative newcomer to servers and hosting websites so I thought I'd ask a simple question here.

To transfer a heroku app to a domain, I looked up the instructions here.

https://devcenter.heroku.com/articles/custom-domains

I then ran

heroku domains: add www.mydomainname.com

Now, when I open the web site it says

This webpage is not available

I also read this snippet on Heroku DevCenter

DNS changes can take several minutes to several days to take effect.
Lowering your DNS TTL ahead of time can minimize, but not eliminate, this 
propagation time.

Does that mean I just have to wait?

I didn't really understand what they meant.

Answer 1

If you already changed your domain name's DNS as described in heroku's instructions, then yes, you just need to wait a bit. If not, then you need to do that first, and then wait a bit.

If your domain uses your registrar's DNS servers, then you would need to consult your registrar's documentation regarding how to create or change the necessary DNS entries. Of course, if you are using DNS servers other than those provided by the registrar, the change would have to be made on whatever DNS servers you actually are using.