I need to be running WordPress Version 3.21 in order to install the OptimizePress theme from the zip file on my computer. How do I update to Version 3.21 or ensure that I am running the most current version of WordPress?
You are posting to the wrong support forum. Support for your software and any advice you need are provided on the WordPress.org support forums and they are here http://wordpress.org/support/ If you don’t have a username account at WordPress.org, click that link and register one on the top right hand corner of the page that opens, so you can post to the correct support forums for your software.
If you are referring to the site linked to your username ie. a free hosted WordPress.com blog then know that Staff do all upgrades here and that third platform is upgraded a month before the upgrades are available to WordPress.ORG users.