Nothing dramatic happens in "Good Evening," and that seems to be the point. The speaker has spent time outside with a little dog, enjoying weather that is milder than it was a month ago, when there was ice. The mood is settled and content, the sort of calm you get at the end of an ordinary day.
The second stanza turns to the dog, who is good company, follows the speaker around, and sits on their lap. The line "I am grateful for what I've got" sums up the feeling: it is a simple thankfulness for small things. In the last stanza the speaker loses track of the hour, wondering if it is late or early, and looks forward to sleep. The closing question, "What else should I have said?", is a gentle, slightly unsure ending. It suggests the speaker feels there is little more to add, because everything they need is already there. The plain language and tidy rhymes suit that quiet, unhurried tone.