how do you open get into a imac intel

You don't, really. They are not considered user-accessible. If you do open it, then later need Apple to repair it, you may find they will refuse service because you opened it.

Search on Google for links to disassembling an iMac of your specific model. You can also check at OWC to see if they have an online tutorial. You can also check ifixit.com for a tutorial.

Disassembling the computer is not trivial.

Up through the 2011 iMacs, getting into the iMac and replacing things was difficult but not at all impossible for the average person. OWC has some great video tutorials on how to open and work on an iMac. The 2012 iMac is considerably more difficult. Personally I would not hesitate to open a 2011 or earlier iMac if it was not under warranty. When mine is past warranty I may well replace the 256gb SSD with a larger one. A 2012 is still under warranty and frankly, I'd buy Applecare and sell it before it ran out of warranty. I got a 2011 refurb instead of buying a 2012.

If you choose to get into an iMac, be sure you have the proper tools and static discharge issues all set before you start.