For networks that support SASL (such as PTirc), do the following to configure your ZNC to identify automatically on login, for each network:
/quote znc *controlpanel SetNetwork Nick $user $network your_nick
/quote znc loadmod sasl (it may already be loaded, especially for PTirc)
/quote znc *sasl set your_nick nick_password
NOTES
Replace your_nick with your IRC nickname on the network and nick_password with your NickServ password.
You must respect this rule as best you can if you want to keep the service.
Basically you have to configure SASL and stay on the #ApexBNC channel at all times.