You can use the PWM module and an interrupt driven software helper to link together several shorter PWM "frames" into a 20-msec servo period with extremely fine pulse width resolution but, unfortunately, the method is probably a bit advanced for a beginner (and some more experienced programmers as well).
Probably better to look at using the CCP module "special event trigger" mode for generating the 1.0 to 2.0 msec pulse and remainder of 20 msec servo period. I believe Pommie has a nice example floating around on the Forum somewhere. I will look for it.
Regards, Mike