uhhh, just so we're in the same page. which atmosphere we're talking about here?
was it a nuance that portraying the characters are currently in a certain situation (like showing the character that they're at the dessert without saying anything about dessert)
or was it about the whole timeline and situation, that let's say you want to make a story that taking place in the future, so you want to give the vibe that everything around is futuristic.
whichever it is, I believe the key point is to knowing it yourself clearly which condition that the characters currently going through. and start going from that as a base.
for example you want to show that the characters are currently in a very awkward situation. I won't tell you to do this "show, don't tell" stuff, but you can just do it in a way you think it works and you're able to pull. like just let one of the character blatantly saying ".....okay, this is awkward" or anything that you can think of to show that the situation is awkward. be it by adding some narrative or adding away some details of the current situation here and there.
It depends on what atmosphere you're trying to add.
Generally, your toolkit will always comprise of the subtleties, such as the setting and the way you describe it, your choice of words, pacing, the small gestures characters do or do not make...
Whenever I want to add a particular atmosphere to something, I think back to moments in life that tend to bring about those feelings and then analyse them for the parts I noticed the most at that time.
If I include similar aspects in my writing, I should be halfway to recreating it for the reader.