make Mavericks USB bootable drive in El Capitan

So my cousin is replacing a dead hard drive in his 24" iMac. They are putting in a 480 gig SSD which should breath some new life in the older machine. Anyways, the store wanted $75 to install the OS. They are gone for a week and a bit so I told them I will just get it all back up and running, they have a time machine backup so basically just need to get something installed so I can restore from time machine. I am assuming I need to install and OS before getting to the startup restore option. I have a disc image of Mavericks and want to create a USB installer. Not sure exactly how to do that, I find instructions for el capitan but not nothing on how to do it from el capitan with a mavericks installer. Whats the best way to make a bootable USB installer of Mavericks from a computer running El Capitan?

via ehMac.ca http://ift.tt/2aJYLk3