How do I change and match(bias) the tubes in my fender super twin reverb guitar amp?

I have bought a new full set of tubes/valves for my 1979 fender super twin reverb guitar amplifier. I can switch the tubes easily enough, but don't know a thing about matching them. I see an adjustable screw at the back saying ';output tubes matching';, but how do I do this correctly to achieve the best tone from my amp, and to ensure that the tubes won't cut or blow. I know very little about electronics. I also live in Dubai, and there are no tube amp specialists whom I can take my amp to.How do I change and match(bias) the tubes in my fender super twin reverb guitar amp?
Take it to someone who knows what they are doing. some older amps still hold a charge big enough to kill you unplugged. good luck