They’re just pronouns, just like “he” and “she” and “her” and “they”, except that they’re relatively new inventions (hence “neo”, meaning new) You use them the exact same way you’d use traditional pronouns.
If someone’s pronouns are “he” and “him”, you say “he went to the shops” and “they gave him a cake”
If their pronouns are “ze” and “zir”, you say “ze went to the shops”, and “they gave zir a cake”
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