You have to undo three screws on the bottom (not all the way,m they are captured screws), lay the machine flat on its screen (a non-marring surface like a towel on a clean desk is recommended). The whole back comes off the machine bottom first, "hinging" up at the top.
Then there are just two angled DIMM sockets to put the RAM in. Warning - do not attempt to install RAM with heat spreaders on them - you'll break the sockets, there isn't room.
The only tricky bit is getting the barbed catches on the top edge to engage as you lay the back of the machine back down on it. Helps to havs a 2nd person just holding the top in place.
Easy job.