Now, create a project, as a receipt the first of the following commands will return something similar to

heroku create   
Creating app... done, ⬢ aqueous-stream-36974
https://aqueous-stream-36974.herokuapp.com/ | https://git.heroku.com/aqueous-stream-36974.git

meaning you have a remote repo. https://aqueous-stream-36974.herokuapp.com/ is, or rather will be the url of your remote application. https://git.heroku.com/aqueous-stream-36974.git is the repo.

Obviously your url, and repo will be different.

Then you initialise a local repo, and link it to your remote repo. Go to your projects folder and do something like:

npx express-generator -v pug --git localnext

cd localnext
git init --initial-branch=main
heroku git:remote -a aqueous-stream-36974
touch README.md
mkdir controllers
mkdir models
git add .
git commit -m "Initial commit"

The heroku git:remote ... is equivalent to you regular git remote add origin ...

Now, go to work and remember that each commit is also a deployment.

From here on the development iterative cycle is:

git add .
git commit -m 'new age initial'

then test locally. When done do

git push heroku main

Verify remotely by https://aqueous-stream-36974.herokuapp.com/.