Can I use microsoft security essentials or firewall antivirus on windows 8.1
thank youYou can't use MSE on any Windows version later than Windows 7, but you don't need to. Windows 8.1 & later already has a built-in tool called "Windows Defender" which includes antivirus --- it's enabled by default and updates itself automatically.
Firewall is also built-in to Windows, though many prefer to use a third-party one for higher degree of manual control & configuration.
As for myself, I don't use any third party online security software. Those built in to Windows 10 have proved to be wholly adequate.