iMac Memory upgrade
If you purchased a iMac in 2012, chances are that you have an iMac Mid-2011 model. You should consider getting more memory to help performance and allow you to do more with iMovie and iPhoto. Most likely that you didn't add memory when you purchased the computer and only have 4GB of memory.
Apple made the Mid-2011 model easy to upgrade the memory, so you don't need to bring it to a dealer or the Apple Store. Certainly if your uncertain about adding memory to the computer, you should consult an expert.
However before you do, watch this video to see how easy it is to install.
This is the memory that is supported in the Mid-2011 model:
DDR3 1333 MT/s (PC3-10600) CL9 SODIMM 204-Pin 1.35V/1.5V Notebook Memory Modules
Crucial is one of the highest rated manufacturers that makes the memory. You can purchase them at Amazon Prime, MacSales.com or BestBuy.com.