Or you can ask posters here where they found their software.
In that case an Internet search might turn up a cloud-storage link or a torrent. Some fitting software is readily available on the manufacturer’s site, but sometimes it’s a bit harder to come by.
In this example one can see that all Marvel models require Target software, and can be programmed with a Noahlink Wireless device (available on Ebay etc.) Many newer aids use that device and it may become a standard.