They apply, the referendum is proof of political support, which is important for the Euc to move forward (if joining the EU is unpopular they don’t want to get involved), then more review and committees are formed.

If all goes well, a few years down the line a formal vote for accession happens, in the EU parliament, and often the country has to have another referendum before it can actually be finalized.

Takes a decade really, and that’s without Hungary being Hungary.