Setting your timezone is important so that you are notified at the right time for any Follow Ups that you have due. This will also ensure that your logged activities have the correct time stamp.
You can access your timezone by clicking on your initials in the top right corner and clicking "Account Settings" from the drop down menu.
When on the "Account settings" page, select your timezone from the dropdown below the email signature field.
Be sure to click "SAVE CHANGES" when you're done.
BOOM - you're all set!