what is the best way to add 2 subdomains to heroku?

Ill start with an apology , i saw a lot of simillar questions here before i posted my question , this one was the closest i found but im still not sure i have the same issue.

im uploading my first app to a nameCheap domain and just want to both www.myapp.co and myapp.co to point to the same app i have on heroku.

I've read the documantation and sucssesfuly added each subdomain seperatly after getting the cName ( deleted the first and then tried the second)

So my question is - what is the right way of using both subdomains ? is it ok to just add 2 subdomains to to the same heroku app and use 2 different cNames ?

TIA