How do I insulate a living area below a former porch
Normally the insulation is on top of the sheetrock, and venting takes place just below the roof boards, or anyway between the roof boards and the top of the insulation - unless you have a lot of space to work with, more insulation is better up until you block the venting, and then it's not.
Given that it's a &quot;converted porch&quot; the high side of the venting may be difficult, or at least involve getting creative, if it butts up against a wall rather than connecting to a vented attic - in which case you'll need to install vents on the top part of the roof surface. Intake vents at the eaves/soffits should be more normal.
Buildings of that age, never assume with respect to insulation - there may be other areas completely lacking it that you'd expect to be insulated.