Well it depends on what kind of reset you are talking about.
To do a "Factory Reset", which shouldn't erase all, but will erase some, data. There should be a small pinhole on the phone. You would need to depress that button with something small, but not sharp (don't want to damage anything) and that should do it.
If you are wanting to do a "Hard Reset", please follow these instructions.
NOTE: Doing this will clear 'all' the data on your phone, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the phone.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the phone...
1. Make sure that the phone is...