Forget "egli" (for human beings) and "esso" (for things). They are outdated and - for sure - you'll never listen to Italians saying "egli" or "esso". You can find "egli" in novels or essays, but I guess you want to learn Italian in its practical usage. Anyway, you can't say "lui" if you want to refer to things. You can imply them or use pronouns like "lo" "la" (as object pronouns) or say the terms again.

Thanks.

I would like to point out that you shouldn't be worried about egli/ella: they're almost never not used in the spoken language (you can find them in books though) and they're used as subject pronouns to refer to a person exclusively. But, as for esso/essa/essi/esse, you can hear them sometimes and certainly you can find them in the written language. They are used to refer to a name of an animal or a thing or even a person that has been previously mentioned. They're particularly useful when referring to things. For instance, I remember a few years ago a well known Italian politician plastered the city with posters for his campaign and on one of them he wrote: "difendiamo l'ambiente: da LUI dipende il nostro futuro" and everybody made fun of him because he should have used ESSO instead.