Worldbuilding for an intergalactic space opera

I’m working on a story set in the distant future of the universe, with intergalactic space travel, alien species and civilizations, super advanced technology, etc. I want to flesh out a whole galaxy to serve as the backdrop for the story I’m telling. <br><br>This seems like the perfect sub for asking questions about things I don’t know the first thing about, or asking for advice on how to approach things. I’ve never tried worldbuilding before, at least not on this scale.