Well, you can add a couple of 90's and simply run it through the wall.
....or you can run it through the roof.
I believe I'd run it through the wall before I'd go straight up two stories to go through the roof.
An 8×8, 2 story shed?
Kind of an odd configuration, but whatever.
I'd go up 1 full length of stove pipe, 90° back to the wall.
I think standard stove pipe is 36".
I'd set the stove 24" from the wall and carry the stove pipe 18" from any exterior wall.
That will keep you from having to work off a ladder or climb something to go through the roof.
Through the wall may cause some draft problems, but nothing that can't be overcome.
It is generally considered a stove pipe should clear the ridgeline of a home by 2 feet.
Good luck!
