Computer & Video Games

hi. my imac is utterly out of memory. i wish to fool around a little mechanism games though there is no rooom for them. we paid for a 500 Gigabyte outmost tough expostulate for my computer. Is there a waay to instal, play, as well as save my diversion to this outmost tough expostulate so my mechanism wouldnt need to make use of any mental recall though a outmost tough expostulate will?? THANK YOU SO MUCH FOR YOUR HELP!!!!!!!!!!!!!!!