Jack up the car on the rear beam, then place the axle stands on the rear seal jacking points. Undo the top nut which I think is 17mm, but you'll need some small adjustable for the top of the shock in case it spins.
Then it's a 18mm for the lower shock bolt. I normally lower the jack a tad so it's not so much pressure on the rear shock when undoing the lower bolt.
Reverse the effect when refitting new ones :smile:
That's how I do it anyway, others may use a different technique. But as
@leeds2592 said, tgere is worse jobs to do. This is a great DIY starter job.