That SSD will likely work. I have two Macs with SSD's one a Samsung and the other from OWC.
Find your iMac and follow the instructions at https://www.ifixit.com/Device/iMac_Intel
Have a can of compressed air handy to clean the dust out while the display is off.
Partition and format the SSD before you install it, GUID partition scheme, Mac OS Extended Journaled format.
Use Carbon Copy Cloner or SuperDuper to clone your existing HDD onto the SSD after you format it.
Either get an inline temperature sensor cable or fan control software because your fans are going to go crazy without the original drive installed.
Take your time and be careful, opening an iMac is not for the faint at heart, but doesn't require a brain surgeon either!