I assume you've let them know that you'd like to visit?
If you are on any sort of business travel you need a letter of invitation from a company based there (doesn't matter if it's not Libyan) [B]and[B] you need a visa and biometric passport.
If it's a private flight you'll need a letter of invitation from a credible person in Libya who will be hosting you to obtain specific permission.
There only used to a handful of their embassies world wide which could issue visas and give specific permissions etc but I don't know what the situation is now.
Either way, unless you are a tourist travelling with a recognised company, there's a lot of running around to do before you even fuel the plane.