When I want to print a painting, it's not possible to print it,
I have a (wireless) network printer, it doesn´t show in the list.
Can you provide more details about the OS version you're running (apparently Windows, based on the 'Group' set for this bug when it was open -- but which?), what kind of printer and driver is being used. Are you using the latest version of Tux Paint (the Group of this bug indicates 0.9.14, but that's very, very old). A screenshot may be helpful.
In the meantime, assigning to John P., who typically maintains & builds the Windows version of Tux Paint.
No follow-up from reported, so closing. Not enough info for us to help. Sorry!