Just got a new SSD installed into my macbook pro, how to use? I have a mid 2012 macbook pro

I just took out the optical drive put my main hdd in its place and installed a 525 gb ssd in the original hard drive slot.

I've been trying to install osx on it for the past 2 hours using alt/option but the computer just boots up on the hdd hard drive even after selecting the usb

Any help is greatly appreciated...as I'm close to throwing my computer out the window.

fyi this did not work.
How to Install OS X on new hard drive on a Late 2012 Mac mini
First boot into your old system. With the SSD plugged in to your system you'll need to run Disk Utility to partition the drive with GUID and format it with a Mac OS Extended (Journaled) partition.
Then Shut down your mac and press the powerbutton again.

Immediately after hearing the Mac boot chime, hold down Command+Option+R – if you see the Apple logo you waited too long and need to reboot and try again.

When you see a spinning globe icon, Internet Recovery mode has been entered with a message saying it can take a while, a progress bar appears as the recovery functions are downloaded.

When finished downloading, you’ll see the “OS X Utilities” screen, choose “Reinstall OS X” to begin the re-installation process of the Mac operating system

Select the destination(SSD) and complete the installation.