If you don't have the ~/.ssh/config file, you can create one yourself and then fill it with the content you need.
You can refer to the video around 0:51
This file is just for simplification. In fact, you can also use:
ssh -i ~/.ssh/my_privK -R 443:localhost:80 v2@connect.ngrok-agent.com http
to replace it, which works as well.
However, if you have the ~/.ssh/config file, it can look like this:
Host MyTest
HostName connect.ngrok-agent.com
User v2
IdentityFile ~/.ssh/
Then the command can be written as:
ssh -R 443:localhost:80 MyTest http
Here, MyTest will be matched with the entry in your ~/.ssh/config file where the Host name is MyTest. From there, it fetches the corresponding User and HostName (in this case, v2 and connect.ngrok-agent.com).
The -i option is omitted in this case, as it refers to the IdentityFile.
Thank you.