Early 2012 Partition Help

My suggestion would be to put the ssd in the optical bay ( I'm assuming you have the optical bay HD kit ). Then connect your old 1tb to your mac via sata to usb , boot holding command plus r , you didn't mention what OSX your running so I will give you two examples .

1.) Yosemite - once in restore console wipe the new ssd with disk utility , then click restore. Your external should show orange and should have two sections pick the bottom as the source , use thr second portion after formatting of your new ssd , then click restore . Be very sure you have the ssd as the destination and not the external as it erases the destination drive again .

2.) El Capitan - same as above hold command plus r to get to recovery , wipe the the new ssd with disk utility , when it finishes highlight its second partition , then click on edit from top left of screen menu , restore and you will get a pop up asking what you want to use as the source .

Put your operating system(s) and applications on the ssd and use the stock 1tb as your storage drive . After you finish the restore and log into the ssd go in applications and disk utility and use it to wipe the old 1tb .