I accidentally deleted mac partition while creating a dual-boot

holding down the option key, as mentioned above, will get you to the 'disk selection screen'. this will show a list of all bootable sources connected to the machine. (holding down the 'C' key will do the same thing, but instead of bringing up a list, it boots directly to the optical drive)

If it is locking up on the apple logo after selecting the boot source, it is not to do with your current hard drive setup, it will be to do with either the install disk you have (it could be corrupt, damaged or from an incompatible range) or you optical drive may be faulty. Can you confirm if you machine was made in Early 2011 or Late 2011? you can identify this by the function symbols over the F3 adn F4 keys on the keyboard. (The early range has 3 boxes within a box, whereas the late just has 3 boxes on a larger scale) the late 2011 range has a network recovery option with lion, which is an easy route that i can explain if you need. otherwise, get a USB installer, or access the machine through target disk mode on another machine (if you have another intel mac around to work with)