The recommended size for optimal ticket printing is 80 mm. You can use any brand and model of ticket printer.
It's not necessary to make any special configuration, that is, if from that computer you can print documents on that printer, you can also print the Gespet software tickets without linking the software with the printer, etc.
If the tickets are not printed, it is because the printer is not configured correctly for that equipment. Follow the manufacturer's instructions to configure and "link" it with that equipment.
If the tickets are printed but the format is not correct (very small / large size, cut text, blurred text, ...) the printer settings vary. In the configuration parameters of your printer you can indicate the size, include your logo to appear on the tickets, the spacing and many other aspects.
If you want the logo to appear on your tickets, you must configure it on the printer, not on the software. Access the printer configuration parameters and configure it.