Ian, in the subject line you wrote this: "How to get REPLY button on each post"
In your "post" you wrote: "None of my screens (am logged in) have a "obvious" way to post a replys? "
So in "permies speak", a post is each small contribution a member writes, and you are correct, each contribution doesn't have it's own button and it's own chain of comments the way a program like Youtube has.
Permies values and promotes perennial threads, so any post you make on an existing thread is added to the very bottom.
Once you find and press the "Post Reply" button that Timothy Norton pointed out, that is what will happen.
However, if you want to comment specifically on someone's post, that is what the "Quote" button is for. On desktop, it's in the row of buttons like the Thumbs up, and the Report! (please press and leave a brief comment if you see spam or nastiness, and staff will come along with their electronic brooms and tidy it up.)
I'm not sure where it is on mobile devices, as I'm a dinosaur. However, if you can find the quote button, you do *not* have to quote the entire post if you only want to refer to a paragraph of it. We appreciate it if in particular, unnecessary photos are deleted, as they take up a lot of space on the page and bandwidth on mobile devices. If the photo is essential to what you want to comment on, then by all means, leave it in place.
We do have a number of very helpful volunteers who use mobile devices, and you've come to the right place to ask questions to help you contribute easily. I think that stating the type of device you're using, can help the helpers?
Permies is a bit unique and the learning curve for some of us is steep, but totally worth the climb!