I assume you have replaced your optical drive with a HD/SSD carrier per this IFIXIT guide: Installing MacBook Pro 13" Unibody Mid 2012 Dual Hard Drive.
There are a few of issued you'll need to work out here before altering your system. First you need to make sure your systems firmware is up to date follow this Apple T/N: About EFI and SMC firmware updates for Intel-based Mac computers. Make sure yours is at this level or newer. I don't recommend moving the HD from its current location as only the HD SATA port has HD crash guard protection.
The next issue is if your system can support the drive you are planning on using. Review this: OWC Data Doubler Take not in the note in Red if you have a MacBookPro8,1 model. It makes no difference who's carrier you used they all face the same problem as the issue is within the logic board of the system. Here you will need a FIXED SATA II (3.0 Gb/s) drive. You can't use a SATA III (6.0 Gb/s) drive or one that auto senses the systems SATA I/O ports speed.
OK, so you are ready to go forward.
I would recommend you first create a bootable USB thumb drive (16 GB) and then copy over to it the OS installer. This will take less time then allowing the system to do internet recovery and you won't need to move the SSD from the optical bay (which is the best place for it). Follow this guide on setting up the USB drive: How to Make an OS X Yosemite Boot Installer USB Drive
If you want to do internet recovery onto your new SSD you will need to put the SSD drive into the HD bay and then boot up the system in recovery mode. Here's an Apple T/N that explains things: About OS X Recovery. After it's running move the SSD back into the optical drive bay and put the HD back in its rightful place.