iMac OS X El Capitán starting up on OS X utilities after erasing untitled disk
So I was trying to factory reset my iMac and erased an Untitled disk reading "511.25 GB SATA Internal Physical Volume OS X Extended" After that I restarted my iMac it started up on the OS X Utilities, I also have been trying to reinstall the OS X El Capitán on my iMac but after verifying my apple id and agreeing to terms it just said that it was temporarily unavailable. I don't want to do to much myself in case I'm just further damaging the iMac. Thank you in advance!
iMac 27″, OS X 10.11