How do I transfer Boot disk from External HDD to newly inserted SSD?

How do I transfer Boot disk from External HDD to newly inserted SSD?

I'm trying to upgrade from my MacBook Pro's original HDD to a SSD. Right
now my external HDD, which I installed OSX Mountain Lion on, has to be
plugged in to boot. If I unplug it, I get a white screen with a flashing
folder icon upon boot up.
I open disk utility and it shows my samsung SSD, which I just
repartitioned to use Mac OS Extended (journaled)
EDIT I click finder and it shows under devices: "OSX" which is the name I
gave my external HDD currently running OSX.. and "Samsung SSD." OSX has
the standard folders on a mac.. Samsung SSD is blank.
How can I get OSX to boot from my SSD rather than the external HDD? Thanks!
Would doing this get it to do that?