if your system permits it, sure you can upgrade from I3 to I7, it all depends on a few things like is your system a desktop or a laptop, what is the make of your desktop motherboard or if a prebuilt system what make/model of the desktop unit. then after verification and assuming you can upgrade to an I7 you will need to know how to take the heatsink off your cpu, have to clean the area of heat paste, insert new cpu properly, apply new heatsink paste, reassemble the heatsink on cpu, and test.
iun theory if a desktop, more than likely possible, if a laptop, sorry not likely possible to upgrade.