Whether you have the basic straight sections or the upgrade awning kit they all come apart in the same fashion, they just slide into each other and should come apart with a simple pull or twist. Often 2 sections might stick a bit from rust and can usually be freed up by gently tapping one end on the grass or a timber board (be careful not to bash it too hard because you don't want to knock the chimney out of shape) while holding the other end, then turn 180 degrees and tapping the opposite side. If it is really rusted together and playing hardball a spray of WD40 or RP7 into the joint then set aside to let it do it's thing for a few hours or overnight will often do the trick. Another good idea is a few gentle taps at the joint with a rubber mallet to loosen up the rust. If all of this fails then chances are that there might be some sap residue holding your chimney together from the inside, in this case heat is the best solution. Start up a decent fire inside your pig then get yourself a pair of leather welding or gardening gloves or some other heavy duty heat proof fabric and try pulling the chimney apart while it is hot, the heat from the fire should melt the sap allowing the chimney to be pulled apart. Also a gentle blast all over the joint with a plumbers propane torch is very effective.