# функция в основном классе:

...

def show_about(self, e=0):
self.dlg = AboutDialog(None)
self.dlg.Show()
return True

...

class AboutDialog(wx.Dialog):
def __init__(self, parent):
wx.Dialog.__init__(self, parent, id=wx.ID_ANY, title=u"About ChaineR", pos=wx.DefaultPosition,
size=wx.Size(400, 125), style=wx.DEFAULT_DIALOG_STYLE)

self.SetSizeHints(wx.DefaultSize, wx.DefaultSize)

bSizer1 = wx.BoxSizer(wx.VERTICAL)

self.m_staticText5 = wx.StaticText(self, wx.ID_ANY,
u"Program is written for work with mnemonic items in tree format\nParticularly can be used for construct Ciceron memory palace\n\nAll rights reserved\nEnjoy!",
wx.DefaultPosition, wx.DefaultSize, 0)
self.m_staticText5.Wrap(-1)
bSizer1.Add(self.m_staticText5, 0, wx.ALL, 5)

self.SetSizer(bSizer1)
self.Layout()

self.Centre(wx.BOTH)