Pull the sheet from the register
A certificate of good standing is the register's word that your firm exists and still trades. In Italy it comes from the Camera di Commercio, the chamber of commerce, which keeps the business register for the province. Ask the Catania chamber for a signed one. To apostille a Certificate of Good Standing in Catania you must hold that signed sheet in your hand.
Chamber first, Prefettura second
A register sheet is a plain state paper, so the Prefettura deals with it. That office is the prefect's local branch of the government, and it adds the apostille: one stamp showing that the signature on your sheet is real. Deeds from a notary and papers from a judge take a different road, to the Procura della Repubblica at the court.
Before you work out how to apostille a Certificate of Good Standing, look at who signed it. A sheet you pulled yourself from the register's web page carries no signature, so the Prefettura has nothing to check. Ask the chamber's desk for the signed version and say it is bound for another country.
Fees and how fresh it must be
The state fee is a tax stamp of €16 per document, and some papers are exempt. That is the apostille cost for a Certificate of Good Standing in Catania on the state side, while the chamber sets its own charge for the sheet. Neither desk promises a fixed wait. Banks and tender boards often want a recent sheet, so order it once your deadline is set rather than long in advance.
Tenders, banks and branches
Firms need this proof when they bid for work abroad, open a bank account in another country, or sign up a dealer who wants to know the seller is real. It also comes up when you set up a branch or send staff overseas. Italy has been in the Hague Convention since 1978. So you can apostille a Certificate of Good Standing in Italy, and a member state will take the stamp as it stands.
Language and the longer route
The stamp covers the signature and not the text, so the reader abroad may ask for a sworn translation of the sheet. Ask that office in writing before you order one. If the country sits outside the Hague Convention, full legalisation of a Certificate of Good Standing in Catania applies instead, which adds the foreign ministry and then a consulate.