Please refer to the guide attached in this article below.
Currently, the only supported thermal printer brand is Epson. The thermal printer that is purchased must have the capability to be connected to the same WIFI network as the iPad running the Oddle Register app. This means that the thermal printer can be connected to the same WIFI network via an ethernet cable or have a WIFI module attached.
We recommend getting the following models from Epson :TM-T88V or TM-T881V.
All thermal printers do not come with the WIFI module or ethernet module installed. The WIFI or ethernet module for the thermal printer must be purchased separately. An example is shown below.
Example of a Thermal Printer Receipt