Testing environment, how to access

I see several other questions just like this, but the answers are not helpful. The question is: how to access a test installation BEFORE changing DNS pointers.

So I have a domain already running on shared hosting. Now I setup my new site on Digital Ocean droplet, for instance. Then I want to bring up my test installation over at DO in my browser… what’s the address?

I’m using Nginx.

http://159.203.xxx.yyy/?

I want to setup the site over at DO, import the data, test it, ONLY THEN do I want to go and change the DNS nameserver records.

Duplicate question.