Making a thumb drive of El Capitan would be the simplest way to approach this!
Boot from the USB Drive. Restart your computer and boot from the USB drive (Press Esc/F8/Del to access the boot selection menu). Use the arrow keys to select Boot OS X Install from Install OS X El Capitan (It should be selected by default). Press the spacebar and select Boot Mac OS X in verbose mode. Using New Disk Utility Clean Install OS X El Capitan from USB Boot Disk. How To Clean Install OS X El Capitan Using Disk Utility. Clean Install OS X El Capit. You can create a bootable USB drive (here are instructions for Yosemite, El Capitan, or older systems) from your iMac, then boot into it on your MacBook Pro using the Option key. Select the disk from the menu, select your language, then choose Disk Utility from the Utility drop-down menu and proceed to reformat it to the right settings. If you have a friend with a Mac that will still run El Capitan, take your drive round to them. Alternatively, if the SuperDrive is still working - those don't necessarily last 13 years either - then buying a Snow Leopard. install CD/DVD on eBay could be your get out of jail free card. As a final, if bulky, alternative, any Apple Store will do. El Capitan Clean Install on Empty Volume with El Capitan Installer This is the easiest method for the clean install. Here, you can install the OS X El Capitan Installer onto an empty volume, or you can use a storage space that has the content which no longer needed and don’t mind removing.
First off, install that upgraded RAM into the iMac as you will need the speed. After you've done that, boot the computer up normally, open the Appstore, and download OS X El Capitan from the Appstore, so that you can make a USB flash drive out of it.
Clean Install El Capitan Without Usb Flash Drive
Once El Capitan finishes downloading, download DiskMakerX from here
This program will automatically create a bootable El Capitan flash drive for you to use to install El Capitan on the computer.
El Capitan Os X Download
After the program finishes and creates your flash drive, turn off the computer, take out the old HDD, and throw in that SSD you bought.
Now that you've done all of that, plug in the flash drive into the Mac and hold down the ALT key and select the flash drive to boot up from the flash drive and install OS X El Capitan onto your mac.
Once it finishes installing you're done! You'll then be presented with the OS X setup screen and you'll be ready to start using your computer!
Hope this helps! Please reply if you have any other questions.
Dec 2, 2015 7:40 PM